JINR Publishing Department: Physics of Elementary Particles and Atomic Nuclei (PEPAN) 2014

Volume 45 (year 2014) , parts: 1 , 2 , 3 , 4 , 5-6
Part 1	up
Akhunzyanov R.R., Shevchenko O.Yu. QCD Analysis of the Semi-Inclusive COMPASS and HERMES Data The first moments of polarized valence parton distribution functions truncated to the wide Bjorken x region 0.004 < x < 0.7 are directly (without any fitting procedure) extracted in the NLO QCD from combined semi-inclusive DIS data of COMPASS and HERMES Collaborations. Two scenarios for fragmentation functions are considered. Applying the proposed original procedure to these results we estimate the contributions of sea u and d quarks to the proton spin, which turn out to be simply zero within the errors.
Ermolaev B.I., Greco M., Troyan S.I. QCD Factorization for the DIS Structure Functions at Small x We suggest a new form of QCD factorization for inclusive processes at high energies and then reduce it to K_T factorization. In turn, K_T factorization can be reduced to collinear factorization when the unintegrated parton distributions have at least one maximum in k. This property of the parton distributions can be checked with studying data of experiment. The sharper the maximum is, the more accurate the transition to collinear factorization can be done. We apply our results to deduce theoretical restriction requirements on fits for parton distributions in both K_T and collinear factorizations contrary to the present situation where the fits are introduced from purely phenomenological consideration so that any formula for them is acceptable if it matches experimental data.
Filip P. Can Mesons Have a Magnetic Moment? The response of pseudoscalar and vector mesons to strong magnetic fields is studied within a simple constituent quark model using analogy with bound states of positronium. Magnetic moments of charged vector mesons K^, D^, B^* are predicted and it is found that mesons have magnetic polarizability. In extremely strong magnetic fields, behaviour of J/ mesons is discussed. We speculate on the existence of an induced magnetic moment of meson.
Ganbold G. Quark-Antiquark Bound States and QCD Running Coupling within Infrared Confinement Bound states of spin-half and spin-one particles are studied within a relativistic quantum-field model based on the infrared confinement. The spectra of quark-antiquark and two-gluon states are determined by master equations similar to the ladder Bethe-Salpeter equations. Masses of light, intermediate and heavy mesons are estimated in a wide range of scale (from hundreds of MeV up to 10 GeV). A new, independent and specific infrared-finite behavior of QCD effective coupling is revealed in the low-energy domain.
Giordano F. (HERMES Collab.) Flavor-Dependent Azimuthal Asymmetries in Unpolarized Semi-Inclusive DIS at HERMES The azimuthal cos _h and cos 2_h modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the HERMES experiment. For the first time, these modulations were determined in a 4-dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins effects.
Goloskokov S.V. Polarized and Transversity GPDs in Kaon Leptoproduction We study the kaon leptoproduction on the basis of the handbag approach. We consider the leading-twist contribution together with the transversity twist-3 effects which were found to be important in the description of pseudoscalar meson production. We present our predictions for the cross section and spin asymmetries in the kaon leptoproduction.
Ivanov N.Ya. How to Measure the Charm Density in the Proton We study two experimental ways to measure the heavy-quark content of the proton: using the Callan-Gross ratio R(x,Q²) = F_L/F_T and/or the azimuthal cos (2) asymmetry in DIS. Our approach is based on the following observations. First, the ratio R(x,Q²) = F_L/F_T and azimuthal cos (2) asymmetry in heavy-quark leptoproduction are stable, both parametrically and perturbatively, within pQCD. Second, both these quantities are sensitive to resummation of the mass logarithms of the type _s ln (Q²/m²). We conclude that the heavy-quark densities in the nucleon can, in principle, be determined from high-Q² data on the Callan-Gross ratio and/or the azimuthal asymmetry. In particular, the charm content of the proton can be measured in future studies at the proposed Large Hadron-Electron (LHEC) and Electron-Ion (EIC) Colliders.
Korotkov V.A. (HERMES Collab.) Measurement of the Spin-Structure Function g₂ and the Semi-Inclusive Double-Spin Asymmetries at HERMES A measurement of the virtual-photon asymmetry A₂ and of the spin-structure function g₂ of the proton are presented for the kinematic range of the HERMES experiment carried out at the HERA electron storage ring at DESY. Semi-inclusive longitudinal double-spin asymmetries provide new insight into the valence quark helicity distributions u and d.
Kotikov A.V., Shaikhatdenov B.G. Perturbative QCD Analysis of the Bjorken Sum Rule We study the polarized Bjorken sum rule at low momentum transfer squared Q² 3 GeV² in the twist-two approximation and to the next-to-next-to-leading order accuracy.
Mekhfi M. Spin versus Helicity: Processes Involving Transversity We construct the spin formalism in order to deal naturally with processes involving transversity which are now of increasing popularity. The helicity formalism which is more appropriate for collision processes of definite helicity has been so far used to also manage processes with transversity, but at the price of computing numerous helicity amplitudes which generally involve unnecessary kinematical variables.
Sharma N., Martnez Torres A., Khemchandani K.P., Dahiya H. Magnetic Moments of the Low-Lying Negative-Parity Resonances We calculate the magnetic moments of the low-lying negative-parity J^P = 1/2^-, 3/2^- resonances within the framework of chiral constituent quark model. The explicit contributions coming from the valence and sea quarks are being calculated.
Pappalardo L.L. Study of TMDs with polarized Beam and/or Targets A Fourier analysis of single- and double-spin azimuthal asymmetries measured at HERMES in semi-inclusive deep-inelastic scattering of unpolarized or longitudinally polarized leptons off tranversely polarized protons is presented for pions and charged kaons. The extracted amplitudes can be interpreted as convolutions of transverse momentum-dependent distribution and fragmentation functions. In particular, the measured double-spin asymmetries are sensitive to the poorly known worm-gear quark distribution _1T .
Selyugin O.V. The Structure of Nucleons and the Description of the Electromagnetic Form Factors The comparison of different sets of PDFs structure functions with the description of the whole sets of experimental data on electromagnetic form factors of the proton and neutron is made in the framework of our model [1] of t dependence of generalized parton distributions (GPDs) and some other models. It is shown that despite a small difference of the description of the inelastic processes by the different sets of PDF, there is an essentially large difference in the description of electromagnetic form factors of the nucleons.
Shevchenko O.Yu., Akhunzyanov R.R. QCD Analysis of DIS and SIDIS Data with Two Alternative Methods The global fit analysis of all published data on DIS and semi-inclusive DIS (SIDIS) asymmetries is performed in the next-to-leading (NLO) QCD order. The respective parameterization on polarized PDFs is constructed. The especial attention is paid to the impact of novel SIDIS data on the polarized distributions of light sea and strange quarks as well as on the polarized gluon distributions. The first moments of these distributions entering the nucleon spin occur surprisingly small quantities. The alternative direct (free of any fitting procedure) method of NLO QCD analysis is elaborated. Method is especially important for analysis of SIDIS data because it allows one to avoid the problems arising in the conventional fitting procedure: functional arbitrariness at initial scale and ambiguities in the error band calculation. Within the alternative method, the central values and uncertainties of the measured asymmetries directly propagate to the central values and uncertainties of the polarized PDFs we are interested in. The method is applied to all existing SIDIS data on pion production for an estimation in NLO QCD of the valence and sea quark contributions to the proton spin. As a result, one arrives at the conclusion that, contrary to the valence contributions, the sea contributions to the proton spin are compatible with zero within the errors.
Leader E., Sidorov A.V., Stamenov D.B. Importance of Fragmentation Functions in Determining Polarized Parton Densities New fragmentation functions (FFs) are extracted from a NLO QCD fit to the preliminary COMPASS data on pion and kaon multiplicities. It is shown that the new kaon FFs are very different from those of De Florian et al. (DSS) and Hirai et al. (HKNS). The sensitivity of the extracted polarized PDFs to the new FFs is discussed.
Soleymaninia M., Khorramian A.N., Moosavinejad S.M., Arbabifar F. QCD Analysis of Fragmentation Functions Considering Double-Spin Asymmetry of SIDIS Processes We extract new sets of pion and kaon fragmentation functions (FFs) at NLO applying combined analysis of single-inclusive electron-positron annihilation and semi-inclusive deep-inelastic lepton-nucleon scattering (SIDIS). We use zero-mass variable-flavor-number (ZM-VFN) scheme in our analysis.
Khandramai V.L., Solovtsova O.P., Teryaev O.V. QCD Analysis of the Bjorken Sum Rule Revisited We present extended analysis of the polarized Bjorken sum rule using the four-loop expression for the coefficient function C_Bj (_s ) available now and the recent low-Q² data from the Jefferson Lab and COMPASS experiments. We demonstrate that the perturbative series for the function C_Bj gives a hint to its asymptotic nature manifesting itself in the region Q² 1 GeV². It is confirmed by the considered integral model for the perturbative QCD correction. We analyze values of higher twist terms extracted from the mentioned data and discuss the interplay between higher orders perturbative and higher twist contributions. We extend our consideration to the Gross-Llewellyn Smith sum rule and investigate the relation between higher twist coefficients in these two sum rules.
Strzik-Kotlorz D., Kotlorz A. DGLAP Evolution of the Truncated Moments of PDFs in Spin Physics We review evolution equations for truncated Mellin moments (TMM) of the parton densities. The main finding of the presented approach is that the nth truncated moment of the parton distribution obeys the DGLAP-like equation, with a rescaled splitting function P'(z) = zⁿP(z). This approach allows one to restrict the analysis to the experimentally available Bjorken-x region. We present some applications of TMM to study the spin structure functions of the nucleon.
Taheri Monfared S., Khorramian Ali N., Haddadi Z., Najafgholi A. The Impact of Target Mass Correction on Polarized Parton Distribution Functions Considering the nonzero mass effect of the target in extracting polarized parton distribution functions (PPDFs) in preasymptotic region is not negligible. We extract PPDFs from available proton structure function data and study the numerical effects of target mass corrections (TMCs). PPDFs with and without this correction are compared.
Teryaev O.V. Can Gluon Spin Contribute to That of Nucleon? The transformation of angular momentum to its Belinfante form requires the smooth behaviour of classical fields at infinity which for the case of quantum operators transforms to the smooth behaviour of matrix elements at small momentum transfers. For the case of quarks, this provides the kinematical counterpart of U_A(1) problem, while for gluons there is a contradiction between kinematics and dynamics governed by Kogut-Susskind pole. This may result in the violation of equivalence principle for nucleons or in the stringent constraints to the strange quark polarization in nucleons, while the most likely outcome would be the impossibility to separate gluon angular momentum to spin and orbital parts in the meaningful way.
Zhun Lu Chiral-Odd TMDs in Drell-Yan Processes We calculate the Boer-Mulders function of the pion by applying the MIT bag model, and compare the result with that from the spectator model. We then study the azimuthal asymmetries contributed by the chiral-odd transverse momentum distributions in pion-nucleon Drell-Yan process at COMPASS and in proton-proton Drell-Yan process at RHIC, J-PARC, E906, and NICA.
Session 2. SPIN IN HADRONIC REACTIONS
Abramov V.V. Polarization Phenomena in Hadronic Reactions Predictions are made in the framework of the effective color field (ECF) model for polarization observables in p + A X, A + A X, and p + Pb pX reactions. The predictions can be checked in the polarization experiments at IHEP (SPASCHARM), JINR (NICA) and BNL (RHIC). Estimates of quark masses and anomalous chromomagnetic quark moments are given.
Alekseev I. (EPECUR Collab.) High Precision Measurements of the Pion-Proton Elastic Scattering and Kaon-Lambda Production in the EPECUR Experiment Study of the pion-nucleon scattering can produce a rich information on the dynamics of the strong interaction and baryon spectroscopy. The EPECUR Collaboration is aimed at the research of baryon resonances in the second resonance region in s-channel via pion-proton elastic scattering and kaon-lambda production.
Corliss R. (STAR Collab.) Recent Star Results on W Production and Asymmetry in Polarized Collisions at = 500 GeV The production of W bosons in longitudinally polarized proton-proton collisions at RHIC is a unique way to study the flavor-dependent spin structure of the proton, since at leading order it couples directly and exclusively to specific quark flavor pairings: u + W⁺ and + d W^-. Measurement of the longitudinal single-spin asymmetry of the electron decay daughters in W production is sensitive to the polarizations of the quarks involved. Results from the first proton-proton collisions at = 500 GeV in 2009 are presented, along with a discussion of the forward-rapidity tracking upgrade.
Jian Deng (STAR Collab.) Longitudinal Spin Transfer to and in Polarized Proton-Proton Collisions at = 200 GeV at STAR The longitudinal spin transfer D_LL of and hyperons is expected to be sensitive to the helicity distribution function of strange (anti)quarks, and to the polarized fragmentation functions. We report new results on D_LL, extracted from = 200 GeV polarized pp collisions recorded at the STAR detector during the 2009 RHIC run. These new results cover midrapidity \|\| < 1.2, with extended p_T up to 6 GeV/c.
Gal C. (PHENIX Collab.) Measurements of the Midrapidity Parity-Violating Spin Asymmetries for W Bosons at PHENIX The parity-violating W single-spin asymmetry, in longitudinally polarized p + p collisions, can give us a clean way to access the - and -polarized parton distribution functions. The current status of the analysis of the 2011 data set and future prospects will be presented.
Yuji Goto (PHENIX Collab.) Inclusive Cross Section and Single Transverse-Spin Asymmetry of Very Forward Neutron Production at PHENIX The cross section and x_F dependence of A_N of very forward neutron production in polarized p + p collisions at = 200 GeV were measured in the PHENIX experiment at RHIC. The measured cross sections were consistent with the x_F scaling claimed by the ISR experiment. Significant negative A_N was observed in the forward region, and no significant backward A_N was observed. We also measured and p_T dependence of A_N of very forward neutron production at from 62.4 to 500 GeV.
Kanazawa K., Koike Y. TWIST-3 Quark-Gluon Correlation Contribution to Transverse Single-Spin Asymmetry for Direct-Photon and Single-Jet Productions in pp Collision We study the contribution of the collinear twist-3 quark-gluon correlation to the transverse single-spin asymmetry in direct-photon and single-jet productions in pp collision. At typical RHIC kinematics we find sizable asymmetries in the forward region of the polarized nucleon while they are almost zero in the backward region. We also find that the soft-fermion pole contribution is vanishingly small, suggesting the measurement of these asymmetries provides us with a unique opportunity to determine the net soft-gluon pole function.
Karyan G. (HERMES Collab.) Charged Hadron Multiplicities at the HERMES Experiment The HERMES Collaboration has measured charge-separated pion and kaon multiplicities in semi-inclusive deep inelastic scattering using a 27.6 GeV electron or positron beam scattering off a hydrogen or deuterium target. The results are presented as a function of the Bjorken variable x_B, the negative squared four-momentum transfer Q², the hadron fractional energy z and its transverse momentum P_h. These data will be very useful to understand the quark-fragmentation process in deep-inelastic hadron electroproduction and will serve as crucial input in the understanding of spin asymmetries in polarized semi-inclusive deep-inelastic scattering.
Koster J. Transverse Single-Spin Asymmetries in Polarized Proton-Proton Collisions at PHENIX The PHENIX experiment probes the transverse spin structure of the proton with asymmetries of particle production in polarized proton collisions. This talk summarizes the measurements of A_N in hadron production at forward and at midrapidities.
Lajoie J. (PHENIX Collab.) Prompt Photon A_N with the PHENIX MPC-EX Detector The PHENIX MPC-EX detector is a Si-W preshower extension to the existing Muon Piston Calorimeters (MPC). The combined detectors will make possible a measurement of the prompt photon single-spin asymmetry A_N in 200 GeV transversely polarized p + p collisions, which will help elucidate the correlation of the transverse motion of valence partons in the proton with the proton spin.
Lee S.H. (PHENIX Collab.) Measurement of A_LL and Cross Section of High-p_T Charged Meson Production for Constraining G at PHENIX PHENIX at RHIC measured invariant differential cross section and double helicity asymmetry A_LL of high-p_T charged pion production in polarized p + p collision at = 200 GeV. Interpretations of preliminary results regarding constraining gluon helicity distribution are discussed.
Nogach L. (A_NDY Collab.) Measurements of Forward Jet Production in Polarized pp Collisions at = 500 GeV The A_NDY project at RHIC was proposed to measure the analyzing power for the Drell-Yan production. Test runs took place during polarized proton operations of RHIC in 2011 and 2012 with a model of the A_NDY apparatus in place. In total, an integrated luminosity of 9 pb^-1 with beam polarization of 50% was sampled. The primary detector components were a hadron calorimeter (HCal) that spanned the pseudorapidity interval 2.4 < < 4.0 and a small electromagnetic calorimeter (ECal). Basic goals for A_NDY test running were to establish the impact of the third interaction region on RHIC performance and to demonstrate HCal calibration. Energy scale of HCal was established using neutral pion reconstruction and checked with hadronic response. In addition, data with a trigger based on HCal energy sum were taken to study jet events. First measurements of analyzing power in the forward jet production are reported.
Chetvertkov M.A., Chetvertkova V.A., Nurusheva M.B., Nurushev S.B., Ridiger A.V. Helicity Conservation Hypothesis and pp-Elastic Scattering TWe propose the helicity conservation model for description of polarization effects in the pp-elastic scattering at asymptotic energies. In this model the complete set of experiments will consist of only three observables. The predictions of model are compared with experimental data.
Oide H. (PHENIX Collab.) Measurement of Longitudinal Single-Spin Asymmetry of W at Forward/Backward Rapidities with PHENIX at = 500-510 GeV Polarized p + p Collisions The PHENIX experiment has collected about 25 pb^-1 longitudinally polarized p + p collisions at = 500 GeV in 2011 run for probing antiquark polarization. In this talk the first preliminary result of A_L is presented.
Pan Y. (STAR Collab.) Transverse Single-Spin Asymmetry Measurements at STAR Transverse single-spin asymmetries A_N are expected to be sensitive to parton polarization and orbital angular momentum contributions to the nucleon spin. Significantly large A_N has been observed in different collision systems such as semi-inclusive deep inelastic scattering (SIDIS) and polarized proton-proton (pp) collisions, indicating a dominant contribution of partonic interactions in the nonperturbative regime. Therefore it is critical to measure A_N in various channels of polarized pp collisions in order to complement SIDIS data and to constrain theoretical models. We report STAR asymmetry measurements on midrapidity hadron-jet and dihadron correlations at = 200 GeV and forward rapidity inclusive hadron production at = 500 GeV polarized pp collisions.
Perry J. Approximation of Jet Axis in Rapidity Separated Dihadron Correlations The PHENIX experiment has observed particle production asymmetries in transversely polarized proton collisons. This talk presents a novel approach for separating the final-state and initial-state components of the observed asymmetries using the existing PHENIX detector.
D'Alesio U., Murgia F., Pisano C. Probing TMDs through Azimuthal Distributions of Pions Inside a Jet in Hadronic Collisions The azimuthal distributions around the jet axis of leading pions produced in the jet fragmentation process in pp collisions are studied within the framework of the so-called generalized parton model. The observable leading-twist azimuthal asymmetries are estimated in kinematic configurations presently investigated at RHIC. It is shown how the main contributions coming from the Collins and Sivers effects can be disentangled. In addition, a test of the process dependence of the Sivers function is provided.
Rossiyskaya N. (COMPASS Collab.) Study of Heavy Hyperons Production in DIS at COMPASS Samples of and hyperons produced in deep-inelastic muon scattering off ⁶LiD target were collected with the COMPASS experimental setup at CERN. The relative yields of ^-(1385), ^-(1385), ⁺(1385), ^-(1321), and ⁺(1321) hyperons decaying into the () were measured. The yield ratios of heavy hyperons to were found to be in the range 3.8-5.6% with a precision of about 10%. The experimental values are used to tune the parameters of the LEPTO Monte-Carlo generator relevant for strange particle production.
Shmakova V. (ANKE Collab.) Measurement of the Spin-Correlation Coefficients A_x,x and A_y,y in the Quasifree np {pp}_s^- Reaction near Threshold at ANKE-COSY A kinematically complete double-polarization measurement of the quasifree np {pp}_s^- reaction near threshold has been performed using the ANKE spectrometer at COSY-Jlich. Here {pp}_s represents a two-proton system with an excitation energy less than 3 MeV. The transversely vector polarized deuteron beam and the internal polarized ANKE hydrogen target were used to determine the spin-correlation coefficients A_x,x and A_y,y. Events from the quasifree np d⁰ reaction were recorded simultaneously and used for both beam and target polarimetry. In addition, the product of the beam and target polarizations could be estimated from the A_y,y coefficient. The storage cell within the polarized target was the main source of background events. Dedicated runs, with no gas in the cell and with the cell filled with N₂ gas, were taken to study the backgrounds. The data analysis procedure and the initial results of the experiment are presented.
Svirida D. (STAR Collab.) Improving Results on Transverse Double-Spin Asymmetries in the CNI Region at STAR Double-spin effects in polarized pp-elastic scattering in the Coulomb nuclear interference (CNI) region are sensitive to small contributions to the nuclear amplitude in addition to the Pomeron exchange dominating at high energies. Measurements of double-spin asymmetries require external luminosity normalization using collision counts for all spin combinations. Several possible sources of such data from various STAR subsystems were thoroughly analyzed to make the best choice. BBC arrays were found to be free of double-spin effects to the level of ~ 2 10^-4 thus leading to the systematic uncertainty ~ 10^-3 in the value of (A_NN + A_SS)/2.
Tsirkov D. (ANKE Collab.) Differential Cross Section and Vector Analyzing Power of the p_pol p {pp}_s⁰ Reaction at 353-700 MeV The reaction p_polp {pp}_s⁰ was studied with the ANKE spectrometer at COSY-Jlich using a polarized beam with the energies of 353, 500, 550, and 700 MeV. The proton pairs {pp}_s were detected at low excitation energy E_pp < 3 MeV, where S wave dominates. The angular dependences of vector analyzing power A_y and differential cross section d/d of the reaction have been obtained for the most of the angular range at 353 MeV and forward angles at the higher beam energies. The partial wave amplitude analysis, done with the 353 MeV results, is important for Chiral Perturbation Theory (CPT) tests at this energy. The data at higher energies detalize the energy dependence of d/d (0) obtained earlier. It allows one to learn about the dynamics of the (1232) resonance excitation in the two-nucleon systems.
Session 3. SPIN PHYSICS WITH PHOTONS AND LEPTONS
Aghasyan M., Avakian H. Extracting TMDs from CLAS12 Data We present studies of double longitudinal spin asymmetries in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator, which includes quark intrinsic transverse momentum within the generalized parton model based on the fully differential cross section for the process. Additionally, we employ Bessel weighting to the MC events to extract transverse momentum-dependent parton distribution functions and also discuss possible uncertainties due to kinematic correlation effects.
Belostotski S.L. (HERMES Collab.) Spin Transfer to and Hyperons in Deep Inelastic Scattering at HERMES Preliminary results on the spin transfer to the and hyperons measured by the HERMES Collaboration are presented. Longitudinal spin transfer directed along the virtual-photon momentum in the rest frame is found to be D_LL = 0.19 0.04(stat.) 0.02(syst.), the transverse component being compatible with zero. For , both longitudinal and transverse components are compatible with zero within statistical errors of 0.1.
Braun Ch. (COMPASS Collab.) COMPASS Results on Transverse Spin Asymmetries in Identified Two-Hadron Production in SIDIS COMPASS is a fixed target experiment at CERN where nucleon spin structure and hadron spectroscopy are investigated using a 160 GeV/c polarized ⁺ beam. An important part of its physics program are the measurements of single-spin asymmetries (SSA) in semi-inclusive deep inelastic scattering (SIDIS) on transversely polarized targets. Data on a deuteron target (⁶LiD) were taken in 2002-2004. After taking the first data on a transversely polarized proton target (NH₃) in 2007, a full year of data taking followed in 2010 to increase precision. The SSA of identified hadron pairs consisting of charged pions and/or kaons from the 2010 data are shown for the first time and compared to model predictions and results from HERMES.
Kageya T. (CLAS Collab.) Measurements of Spin Observables in Pseudoscalar Meson Photoproduction Using Polarized Neutrons in Solid HD A measurement of pseudoscalar meson photoproduction from longitudinally polarized solid HD has been carried out with the CLAS at Thomas Jefferson National Accelerator Facility (Jlab) with circularly and linearly polarized photon beams. The aim is to measure a complete set of spin observables for the neutron simultaneously from the same experiment. As a polarized neutron, deuteron in HD was used. Preliminary asymmetries are shown for the ^- channel.
Makke N. (COMPASS Collab.) Study of the Hadronization Process from Single-Hadron and Hadron-Pair Production in SIDIS at COMPAS Recent results on single-hadron and hadron-pair multiplicities measurement in semi-inclusive deep inelastic muon scattering on nuclear target at the COMPASS experiment at CERN are presented and discussed.
Martin A. (COMPASS Collab.) COMPASS Results on Collins and Sivers Asymmetries for Charged Hadrons The study of transverse spin and transverse momentum effects is an important part of the scientific program of COMPASS - a fixed target experiment at the CERN SPS taking data since 2002. The studies are carried on by measuring the hadrons produced in deep inelastic scattering (DIS) of 160 GeV/c muons off different targets. Among the possible asymmetries in the hadron azimuthal distributions, particularly interesting are the Collins and Sivers asymmetries which the COMPASS Collaboration has measured using transversely polarized deuteron and proton targets. Here new results for charged pions and kaons obtained from the 2010 run with a transversely polarized proton target are presented for the first time.
Murray M. (HERMES Collab.) DVCS at HERMES This talk explores the impact that the HERMES experiment has had regarding knowledge of the Deeply Virtual Compton Scattering (DVCS) process. We discuss the various measurements that HERMES has contributed to the library of DVCS knowledge [1-3], with focus, in particular, on the recent high-precision beam spin and charge asymmetries [4].
Nefedov Yu. (BES-III Collab.) Recent Results of the BES-III Experiment The BES-III experiment in Beijing takes data in tau-charm domain since 2009. For the moment, the world largest samples of J/, (3686), (3770), and (4040) data have been collected. The current status of the BES-III experiment is presented. The overview of recent results on light hadron, charmonium, and charm physics is given.
Pappalardo L.L. The TMD Program at CLAS and CLAS12 Transverse-momentum-dependent parton distributions (TMDs) are crucial ingredients for a complete understanding of the dynamics of confined partons. They allow for a 3-dimensional description of the nucleon in momentum space, and could provide insights into the yet unmeasured quark orbital angular momentum. At CLAS several TMDs are explored in Fourier analysis of azimuthal asymmetries measured in semi-inclusive DIS. An overview of the main CLAS results as well as selected CLAS12 projected results is presented.
Paremuzyan R.G. Timelike Compton Scattering at JLab It is demonstrated that with exclusive final state, data from electron scattering experiments that are recorded with loose trigger requirements can be used to analyze photoproduction reactions. A preliminary results on Timelike Compton Scattering using the electroproduction data from the CLAS detector at Jefferson Lab are presented. In particular, using final state (pe^-e⁺) photoproduction of vector mesons and timelike photon is studied. Angular asymmetries in Timelike Compton Scattering region are compared with model predictions in the framework of Generalized Parton Distribution.
Parsamyan B. (COMPASS Collab.) Six «Beyond Collins and Sivers» Transverse Spin Asymmetries at COMPASS COMPASS is a fixed-target high-energy physics experiment at the SPS at CERN [1]. One of the important objectives of the experiment is the exploration of the transverse spin structure of the nucleon via spin-dependent azimuthal asymmetries in single-hadron production in deep inelastic scattering of polarized leptons off transversely polarized target. For this purpose, a series of measurements were made in COMPASS, using 160 GeV/c longitudinally polarized muon beam and transversely polarized ⁶LiD (in 2002, 2003, and 2004) and NH₃ (in 2007 and 2010) targets. Till now main attention was focused on Collins and Sivers asymmetries, and obtained results play an important role in the general understanding of the three-dimensional nature of the nucleon in terms of Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs) and Fragmentation Functions (FFs). In addition to these two measured leading-twist effects, the SIDIS cross section counts six more target transverse spin-dependent azimuthal effects, which have their own well-defined leading- or higher-twist interpretation in terms of QCD parton model. So far COMPASS presented preliminary results for these asymmetries from deuteron [2,3] and «proton-2007» data [4]. In this contribution we review the results obtained with the last «proton-2010» data sample.
Punjabi V. The Proton Form-Factor Measurements at Jefferson Lab, Past and Future Use of the double-polarization technique to obtain the elastic nucleon form factors has resulted in a dramatic improvement of the quality of two of the four nucleon electromagnetic form factors, G_Ep and G_En. It has also changed our understanding of the proton structure, having resulted in a distinctly different Q²-dependence for both G_Ep and G_Mp, contradicting the prevailing wisdom of the 1990s based on cross-section measurements, namely that G_Ep and G_Mp obey a «scaling» relation G_Ep ~ G_Mp. A related consequence of the faster decrease of G_Ep revealed by the Jefferson Lab (JLab) polarization results was the disappearance of the early scaling F₂/F₁ ~ 1/Q² predicted by perturbative QCD. In three experiments, GEp(1), GEp(2), and GEp(3), in Halls A and C at JLab, the ratio of the proton's electromagnetic elastic form factors, G_Ep/G_Mp, was measured up to four-momentum transfer Q² of 8.5 GeV² with high precision, using the recoil polarization technique. The initial discovery that the proton form-factor ratio measured in these three experiments decreases approximately linearly with four-momentum transfer, Q², for values above 1 GeV², was modified by the GEp(3) results, which suggests a slowing down of this decrease. There is an approved experiment, GEp(5), to continue these measurements to 15 GeV². A dedicated experimental setup, the super bigbite spectrometer (SBS), will be built for this purpose. It will be equipped with a new focal plane polarimeter to measure the polarization of the recoil protons. In this presentation, I will review the status of the proton elastic electromagnetic form factors, mention succinctly a number of theoretical approaches to describe results and show some features required for the future GEp(5) experiment.
Sbrizzai G. Unpolarized Azimuthal Asymmetries in SIDIS at COMPASS The study of the spin structure of the nucleon and of the effects due to the quarks transverse momentum are part of the scientific program of COMPASS, a fixed target experiment at the CERN SPS. The azimuthal modulations which appear in the cross section of SIDIS off unpolarized targets give insight into the intrinsic momentum structure of the nucleon and on the possible correlation between transverse spin and transverse momentum of the quarks. We present the results for the amplitudes of the cos(), cos(2), and sin() modulatuions (where is the azimuthal hadron angle in the gamma-nucleon system) obtained from the COMPASS data collected with a 160 GeV/c positive muon beam impinging on a deuteron target. The amplitudes are measured for both positive and negative hadrons, and the results on the dependence of the relevant kinematical variables obtained after a multidimensional analysis are also presented.
Sokhan D. (CLAS Collab.) Deeply Virtual Compton Scattering from the Neutron with CLAS and CLAS12 Generalized Parton Distributions (GPDs) offer an insight into the three-dimensional structure of the nucleon and its internal dynamics, relating the longitudinal momentum of quarks to their transverse position. A very effective means of accessing GPDs is via measurements of cross sections and polarization asymmetries in Deeply Virtual Compton Scattering (DVCS). In particular, the beam-spin asymmetry (BSA) in DVCS from the neutron is especially sensitive to angular momentum of the up- and down-quarks, and its measurement therefore has potential to shed important light on the puzzle of nucleon spin. We present a preliminary extraction of BSA from a recent experiment using a 6 GeV electron beam and the CLAS detector at Jefferson Laboratory and introduce the Central Neutron Detector to be integrated with CLAS12 for the exclusive measurement of neutron DVCS at 11 GeV, made possible by the Jefferson Lab upgrade.
Yaschenko S. (HERMES Collab.) An Overview of Recent DVCS Results at HERMES The HERMES experiment at DESY, Hamburg, collected unique data on Deeply Virtual Compton Scattering (DVCS) utilizing the HERA polarized electron or positron beams with an energy of 27.6 GeV and longitudinally or transversely polarized or unpolarized gas targets (H, D or heavier nuclei). For the last two years of HERA running, a recoil detector was installed to improve the selection of DVCS events by direct measurement of the recoil protons. Recent HERMES results on DVCS off the hydrogen target and on associated processes ep ep⁰ and ep ep⁺ in the -resonance region obtained with the recoil detector, are presented.
Zemlyanichkina E. (COMPASS Collab.) Longitudinal Spin Structure of the Nucleon at COMPASS (SPS CERN) We present new results on longitudinal inclusive double-spin asymmetry A_1,p(x) in deep-inelastic muon-proton scattering and proton spin-dependent structure function g₁^p(x,Q²). New COMPASS data on longitudinal polarized NH₃ target were collected during the year 2011 with the beam of positive muons with energy E = 200 GeV. Kinematical threshold Q² 1 (GeV/c)² and the fractional energy 0.1 < y < 0.9 allow us to cover low-x region up to 0.025.
Session 4. SPIN PHYSICS IN NUCLEAR REACTIONS AND NUCLEI
Baru V. Status and Recent Developments in NN NN We present a summary of the recent developments in pion production in NN collisions within chiral effective field theory.
Gotta D., Covita D.S., Anagnostopoulos D.F., Fuhrmann H., Gorke H., Gruber A., Hirtl A., Ishiwatari T., Indelicato P., Le Bigot E.-O., Nekipelov M., Pomerantsev V., Popov M., dos Santos J.M.F., Schmid Ph., Simons L.M., Trassinelli M., Veloso J.F.C.A., Zmeskal J. Precision Measurement of the (3p-1s) X-Ray Transition in Muonic Hydrogen The (3p-1s) X-ray transition to the muonic hydrogen ground state was measured with a high-resolution crystal spectrometer. The assumption of a statistical population of the hyperfine levels of the muonic hydrogen ground state was directly confirmed by the experiment and measured values for the hyperfine splitting can be reported. The measurement supplements studies on line broadening effects induced by Coulomb de-excitation hindering the direct extraction of the pion-nucleon scattering lengths from pionic hydrogen and deuterium X-ray lines.
Hanretty C. Exclusive Study of Deuteron Electrodisintegration near Threshold The study of threshold electrodisintegration of and elastic scattering on the only stable two-nucleon system, the deuteron, can reveal specific aspects of the NN interaction. The simplicity of electrodisintegration along with the simplicity of the deuteron makes this study most appropriate for revealing these interactions. By using an incident beam of polarized electrons and by measuring the polarization of the recoiling proton, the ratio of the electric (G_E) and magnetic (GM) form factors for d(,e')n (and p(,e')) reactions may be extracted. This experiment was conducted in Hall A at Jefferson Lab in Newport News, Virginia, using a beam of polarized electrons provided by the CEBAF Accelerator incident on a liquid deuterium (and hydrogen) target. The scattered electron and the recoiling (polarized) proton were detected using the High Resolution Spectrometers of Hall A. To determine the polarization of the recoil proton, an analyzing material was placed perpendicular to the protons trajectory through the spectrometer, in front of a set of straw chambers. Due to the spin-orbit interactions involved in the scattering of the proton from the analyzer material, asymmetries seen in the distribution of events detected by these straw chambers reveal the polarization of the recoil proton. By tracking the spin procession of the polarized protons from the straw chambers back to the target, the transferred and induced polarization of the proton may be determined. The (double-spin) asymmetries observed in the straw chambers will first be studied for the well-known elastic p(,e') process and compared to the asymmetries for d(,e')n (x_B = 1). The analysis will then be repeated to determine how these asymmetries change with increasing x_B (to the kinematic limit for deuteron electrodisintegration).
Ladygina N.B. Spin Effects in the dd ³He n Reaction at Intermediate Energies The dd ³He n reaction is considered at the energies between 200 and 520 MeV. The calculations are performed within relativistic multiple scattering model based on the Alt-Grassberger-Sandhas equations. The angular dependences of the differential cross section and vector and tensor analyzing powers are given in comparison with the experimental data.
Sekiguchi K., Okamura H., Wada Y., Miyazaki J., Taguchi T., Gebauer U., Dozono M., Kawase S., Kubota Y., Lee C.S., Maeda Y., Mashiko T., Miki K., Sakaguchi S., Sakai H., Sakamoto N., Sasano M., Shimizu Y., Takahashi K., Tang R., Uesaka T., Wakasa T., Yako K. Complete Set of Deuteron Analyzing Powers for dp Elastic Scattering at Intermediate Energies With the aim of clarifying roles of the 3NFs in nuclei, experimental programs with polarized deuteron beams at intermediate energies are in progress at RIKEN RI Beam Factory. As the first step, we have measured a complete set of deuteron analyzing powers (iT₁₁, T₂₀, T₂₁, T₂₂) in deuteron-proton elastic scattering at 250 and 294 MeV/nucleon. The obtained data are compared with the Faddeev calculations based on the modern nucleon-nucleon forces together with the Tucson-Melbourne'99, and Urbana IX three nucleon forces.
Thrngren Engblom P. (ANKE and PAX Collab.) A Complete Low-Energy Polarized Proton-Deuteron Breakup Experiment An experiment at low energy will be done at the COSY cooler synchrotron and storage ring in order to study the three-particle final states of proton-deuteron scattering reactions measuring a complete set of single and double spin observables over large areas of phase space. The physics objective is to test the predictive power of chiral effective field theory at an energy where convergence is guaranteed and few previous measurements exist. A direct comparison between theoretical predictions and experimental data will be enabled by the use of the so-called sampling method.
Uzikov Yu.N., Haidenbauer J. Spin Dependence of the Interaction of Antiprotons with the Deuteron Elastic scattering of antiprotons on the deuteron is studied within the Glauber-Sitenko theory accounting for the single and double scattering mechanisms and the full spin dependence of the transition matrix element. Differential cross sections, analyzing powers and total polarized cross sections are calculated for antiproton beam energies between 50 and 300 MeV using the Jlich models for the interaction.
Session 5. FUNDAMENTAL SYMMETRIES AND SPIN PHYSICS BEYOND THE STANDARD MODEL
Asahi K., Ichikawa Y., Chikamori M., Ohtomo Y., Hikota E., Suzuki T., Inoue T., Furukawa T., Yoshimi A., Suzuki K., Nanao T., Miyatake H., Tsuchiya M., Yoshida N., Shirai H., Ino T., Ueno H., Matsuo Y., Fukuyama T. Search for Electric Dipole Moment in ¹²⁹Xe Atom Using a Nuclear Spin Oscillator We aim to measure the electric dipole moment (EDM) of a diamagnetic atom ¹²⁹Xe using an optical-detection nuclear spin maser technique. The relation of EDM in a diamagnetic atom to nuclear Schiff moment and fundamental sources generating it is discussed, and the present status for the development of our experimental setup is presented.
Burinskii A. What Tells Gravity on the Shape and Size of an Electron Gravitational field of an electron, fixed by experimental values of its mass, spin, charge and magnetic moment, is given by the metric of Kerr-Newman (KN) solution. Unexpectedly, this metric contains a singular ring of the Compton radius, which should be regulated resulting in a weak and smooth source. The consistent source takes the form of an oblate vacuum bubble, bounded by a closed string of the Compton radius. The bubble turns out to be relativistically rotating and should be filled by a coherently oscillating Higgs field in a false vacuum state. The Compton size of the bubble shrinks sharply to a «point» for relativistic particle.
Chernitskii A.A. Electromagnetic Soliton-Particle with Spin and Magnetic Moment Electromagnetic soliton-particle with both quasi-static and quick-oscillating wave parts is considered. Its mass, spin, charge, and magnetic moment appear naturally when the interaction with distant solitons is considered. The substantiation of Dirac equation for the wave part of the interacting soliton-particle is given.
Ginzburg I.F. Precise Measuring Mass and Spin of Dark Matter Particles at ILC via Singularities in the Single Lepton Energy Spectrum We consider models in which stability of Dark Matter particles D is ensured by the conservation of the new quantum number, called D-parity here. Our models contain also charged D-odd particle D. We propose method for precision measuring masses and spin of D-particles via the study of energy distribution of single lepton (e or ) in the process e⁺e^- D⁺D^- DDW⁺W^- with the observable state dijet + (or e) + nothing. It is shown that this distribution has kinematically determined singular points (upper edge and kinks or peak). Measuring of their positions allow one to determine precisely masses of D and D. After this, even a rough measuring of corresponding cross section allows one to determine the spin of D particles.
Gorbunov I.N., Shmatov S.V. (CMS Collab.) Measurement of the Forward--Backward Asymmetry of ⁺^- Pairs in CMS The measurement of the forward-backward asymmetry A_FB and the effective weak mixing angle with the Drell-Yan process at the LHC is presented. The samples of 2011 collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5 and 1.1 fb^-1, were used. The results are consistent with the Standard Model expectations.
Groote S., Kner J.G., Tuvike P. The Decays of On-Shell and Off-Shell Polarized Gauge Bosons into Massive Quark Pairs at NLO QCD We discuss the polar angle decay distribution in the decay of on-shell and off-shell polarized (W,Z) gauge bosons into massive quark pairs. In particular, for the off-shell decays in H (W,Z) + (W^,Z^) ( q₁₂) it is important to keep the masses of the charm and bottom quarks at their finite values since the scale of the problem is not set by m² _W,Z but by the off-shellness of the gauge boson which varies in the range (m₁ + m₂)² q² (m_H - m_W,Z)².
Leacock J. (Qweak Collab.) Qweak, N , and Physics beyond the Standard Model The data-taking phase of the Qweak experiment ended in May of 2012 at the Thomas Jefferson National Accelerator Facility. Qweak aims to measure the weak charge of the proton, Q^p_W , via parity-violating elastic electron-proton scattering. The expected value of Q^p_W is fortuitously suppressed, which leads to an increased sensitivity to physics beyond the Standard Model.
Gorbatenko M.V., Neznamov V.P. Stationary Bound States of Dirac Particles in Collapsar Fields It is the first time stationary bound states of elementary spin 1/2 particles that do not decay with time are obtained for a Schwarzschild gravitational field using a self-conjugate Hamiltonian with a flat scalar product in a wide range of gravitational coupling constant. In order to obtain a discrete energy spectrum, we introduce a boundary condition such that the current density of Dirac particles near the «event horizon» is zero.
Obukhov Yu.N., Hehl F.W. Quantum Gravity Model with Fundamental Spinor Fields We discuss the possibility that gravitational potentials (metric, coframe and connection) may emerge as composite fields from more fundamental spinor constituents. We use the formalism of Poincar gauge gravity as an appropriate theoretical scheme for the rigorous development of such an approach. We postulate the constitutive relations of an elastic Cosserat type continuum that models spacetime. These generalized Hooke and MacCullagh type laws consistently take into account the translational and Lorentz rotational deformations, respectively. The resulting theory extends the recently proposed Diakonov model. An intriguing feature of our theory is that in the lowest approximation it reproduces Heisenberg's nonlinear spinor model.
Andreev V.V., Pankov A.A. Distinguishing Indirect Signatures of New Physics at ILC with Polarized Beams: Z' versus Anomalous Trilinear Gauge Couplings We examine the sensitivity of the e⁺e^- International Linear Collider (ILC) for probing the Z-Z' mixing in W-pair production process and its capability of distinguishing observable effects of the Z' from analogous ones due to competitor models with anomalous trilinear gauge couplings (AGC) that can lead to the same or similar new physics experimental signatures.
Rathmann F., Saleev A., Nikolaev N.N. (JEDI and srEDM Collab.) Search for Electric Dipole Moments of Light Ions in Storage Rings The Standard Model (SM) of Particle Physics is not capable of accounting for the apparent matter-antimatter asymmetry of our Universe. Physics beyond the SM is required and is searched for by (i) employing highest energies (e.g., at the LHC), and (ii) striving for ultimate precision and sensitivity (e.g., in the search for electric dipole moments (EDMs)). Permanent EDMs of particles violate both time reversal (T) and parity (P) invariance, and are via the CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics beyond the SM, and pushing upper limits further provides crucial tests for any corresponding theoretical model, e.g., SUSY. Direct searches of proton and deuteron EDMs bear the potential to reach sensitivities beyond 10^-29 e cm. For an all-electric proton storage ring, this goal is pursued by the US-based srEDM collaboration [2], while the newly found Jlich-based JEDI collaboration [1] is pursuing an approach using a combined electric-magnetic lattice which shall provide access to the EDMs of protons, deuterons, and ³He ions in the same machine. In addition, JEDI has recently proposed to perform a direct measurement of the proton and/or deuteron EDM at COSY using resonant techniques involving Wien filters.
Obukhov Yu.N., Silenko A.J., Teryaev O.V. Dirac Particle Spin in Strong Gravitational Fields Dynamics of the Dirac particle spin in general strong gravitational fields is discussed. The Hermitian Dirac Hamiltonian is derived and transformed to the Foldy-Wouthuysen (FW) representation for an arbitrary metric. The quantum mechanical equations of spin motion are found. These equations agree with corresponding classical ones. The new restriction on the anomalous gravitomagnetic moment (AGM) by the reinterpretation of Lorentz invariance tests is obtained.
Tanaka S., Nakaya Y., Ninomiya K., Nishio H., Onishi J., Openshaw R., Pearson M., Totsuka Y., Murata J. MTV-G Experiment: Probing Non-Standard Strong Gravitational Field at Nuclear Scale Using Geodetic Precession A new experiment named MTV-G, probing a large electron spin precession due to a possible strong gravitational field, predicted by large extra dimension model, was started at TRIUMF in 2011. In an electron-nuclear scattering experiment, a strong gravitational field is tested as a large spin precession effect caused by geodetic precession predicted by general relativity theory as a result of a warped space-time around nuclei. Experimental design using spin polarized electron source and Mott-spin analyzer, commissioning experiment and the preliminary results are described.
Tanuma R., Baba H., Ninomiya K., Nakaya Y., Tanaka S., Totsuka Y., Murata J. A New FPGA-Based Trigger/DAQ System for the MTV Experiment at TRIUMF A new FPGA-based data acquisition (DAQ) and trigger combined system is developed for the MTV experiment (Mott polarimetry for T-Violation experiment). The MTV experiment measures backward Mott scattering events by detecting the incident and scattered tracks using a drift chamber. For the backward scattering probability is less than 0.1%, efficient triggering system is required to select the desired events. An intelligent Level-2 trigger system reading hitting pattern together with its digital readout system is built in a custom FPGA system. In this paper, design overview and results from performance tests are described.
Totsuka Y., Baba H., Behr J.A., Iguri T., Ikeda M., Kato T., Kawamura H., Kishi R., Levy C.D.P., Nakaya Y., Ninomiya K., Nishio H., Onishi J., Openshaw R., Pearson M., Seitaibashi E., Tanaka S., Tanuma R., Toyoda T., Watanabe K., Murata J. First Result from the MTV Experiment at TRIUMF Searching T-Violation in Nuclear Beta Decay The MTV experiment (Mott polarimetry for T-Violation experiment) has been running since 2009 at TRIUMF, which aims to search a large nonstandard T-violation in polarized nuclear beta decay. Existence of transverse polarization of electrons emitted from polarized ⁸Li nuclei, which are produced at TRIUMF-ISAC and stopped inside an aluminum stopper, is investigated. We utilize a Mott polarimeter consisting of a planer drift chamber, measuring backward scattering left-right asymmetry from a thin lead analyzer foil. In this paper, preliminary results from the first physics run performed in 2010 are described.
Tsentalovich E.P. (nEDM Collab.) The nEDM Experiment at the SNS The nEDM collaboration proposes to measure the neutron electric dipole moment at the Spallation Neutron Source (Oak Ridge National Laboratory). The nEDM is a clear signature of CP violation. According to the Standard Model, the nEDM is very small (~ 10^-31 e cm), but many theories predict much higher values. In the proposed experiment, polarized cold neutrons from the SNS would be trapped in liquid helium at a temperature of about 400 mK. The neutron spin would precess in a very uniform magnetic field (H ~ 30 mG), and the experiment would measure the change in the precession frequency when a very strong electric field (E ~ 50 kV/cm) is applied. Polarized ³He atoms serve as a co-magnetometer. The goal of the experiment is to measure the nEDM with an accuracy of ~ 9 10^-28 e cm, which is more than an order of magnitude better than existing results.
Tsytrinov A.V., Pankov A.A. Unique R-Parity Violating Sneutrino Exchange Signatures at e⁺e^- Linear Colliders with Polarized Beams We examine the possibility of uniquely identifying the indirect effects of s-channel R-parity violation sneutrino exchange against other kinds of new physics that can be parametrized by the four-fermion contact interactions, by means of double polarization asymmetry at the International Linear Collider with both e⁺e^- beams being polarized.
Yeletskikh I., Bednyakov V., Chizhov M. *Search for Z Boson at ATLAS Detector** We present the results of the search for new excited Z* boson at ATLAS detector in 2011. Results are based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fb^-1 in the dielectron channel and 5.0 fb^-1 in the dimuon channel. Since good agreement between experimental data and expectation of the Standard Model is observed in both channels, the existence of Z* is excluded with 95% confidence level for all masses below 2.20 TeV. The plans for Z* search in 2012 are discussed.
Session 6. ACCELERATION, STORAGE, AND POLARIMETRY OF POLARIZED BEAMS
Bazilevsky A., Fischer W. Impact of 3D Polarization Profiles on Spin-Dependent Measurements in Colliding Beam Experiments We derive the influence of 3-dimensional polarization profiles on the measured polarization in polarimeters, as well as the observed polarization and the polarization-weighted luminosity (figure of merit) in single- and double-spin measurements in colliding beam experiments.
Ciullo G. (PAX Collab.) Polarization of Stored Beam by Spin-Filtering at COSY In the challenging aim to achieve polarized antiproton, the PAX collaboration performed dedicated measurements of the spin-dependent polarizing cross section for pp scattering at COSY. The result, under a very nice control of the process, agrees with the theoretical previsions and confirms the pursuability of the spin-filtering for polarizing antiprotons.
Filatov Yu.N., Kovalenko A.D., Butenko A.V., Kondratenko A.M., Kondratenko M.A., Mikhaylov V.A. Polarized Proton Beam Acceleration at the Nuclotron with the Use of the Solenoid Siberian Snake The possibility of polarized protons acceleration up to 6 GeV at the Nuclotron is analyzed. Proton beam acceleration by application of full and partial Siberian Snakes is considered. Compensation of the betatron coupling introduced by the solenoids is done by a compact insert of quadrupoles with a certain symmetry of their tilt angles around the orbit direction. Such a scheme has a shorter total length of the quadrupoles than the known compensation schemes. The Snakes installed within one, 3.2 m long, or two, 2 3.2 m long, straight sections of the Nuclotron lattice are considered.
Kurilkin P.K., Ladygin V.P. Deuteron Beam Polarimetry at the Nuclotron The scheme of the deuteron beam polarization measurements at Nuclotron is presented. A deuteron beam polarimeter based on the spin-asymmetry measurements in the dp-elastic scattering at large angles in center-of-mass system has been constructed at the internal target station at the Nuclotron of JINR. This polarimeter is planned to be used for the measurements of the vector and tensor components of deuteron beam polarizations at the energies of 270-2000 MeV, simultaneously. Details on the low-energy polarimeters are also discussed.
Makdisi Y. Thoughts on Polarimetry for ³He Beams at RHIC The Relativistic Heavy Ions Collider (RHIC) has accelerated polarized proton beams for physics since 2001. As a part of the future eRHIC program and in order to enhance access to the down quark, a program to accelerate polarized ³He in the AGS and RHIC is envisioned. To that end, a polarized ³He source is being built at MIT. This will be installed on the BNL EBIS source in preparation for injection into the booster and AGS. As an early exercise, in June 2012, unpolarized ³He beams have been accelerated in the AGS. This paper will peruse some potential ideas for ³He polarimetry and calibration that could be utilized at the AGS as well as RHIC. The current proton polarimetry program serves as a guide.
Nass A. (PAX Collab.) Spin Filtering at COSY and Perspectives for PAX The high physics potential of experiments with stored polarized antiprotons led to the proposal of the PAX [1] experiment (Polarized Antiproton eXperiment) for the High Energy Storage Ring (HESR) of the new FAIR facility at GSI (Darmstadt/Germany). It is proposed to polarize a stored antiproton beam by means of spin filtering by a polarized hydrogen gas target. The feasibility of spin filtering with protons using a transversely polarized hydrogen gas target has been demonstrated in the FILTEX experiment [2] and recently confirmed at the COSY ring in Jlich. A spin-filtering experiment using a longitudinally polarized hydrogen gas target is planned after the installation of a Siberian Snake in 2014. Further measurements including the investigation of pd-breakup reactions [3] and a test of the time reversal (TRIC) [4] are planned using the developed experimental setup. A proposal for a spin-filtering experiment with antiprotons at AD/CERN [5] has been submitted to the CERN SPS committee to investigate the spin-dependence of the and interaction. This knowledge is necessary to properly design a dedicated antiproton-polarizer ring.
Podolyako F., Sorokin I., Vizgalov I., Zelenski A., Atoian G., Klenov V. Studies of Basic Limitations on Production, Transport and Acceleration of the High-Intensity Polarized H^- Beam in the RHIC Polarized Ion Source Basic limitations on the high-intensity polarized H^- ion beam production and transport were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapor-jet ionizer cell. The energy dependence of space-charge effects on the beam instabilities and losses was studied and described in the model of synthetic H⁺-H^- beam transport. A xenon gas admixture to the H^- ion production cell and beam transport line greatly improves the space-charge compensation, which is also successfully described in the simulations. These studies are the part of the polarized source upgrade project for RHIC.
Ptitsyn V., Khalil N. Calculation of Spin Resonance Harmonics in an Accelerator with Snakes In this work, the ASPIRRIN code has been extended to provide the calculation of resonance harmonics for the case of machine with Siberian Snakes and spin rotators. Examples are shown for RHIC accelerator, including the case of the configuration with six Snakes per RHIC ring.
Koop I.A., Otboyev A.V., Shatunov P.Yu., Shatunov Yu.M. Two Examples of In-Flight Spin Flippers In precise experiments with polarized beam it very often appears a necessity to change beam polarization on opposite. If such operation does not change other beam parameters, it helps to avoid or minimize some systematic errors. It is especially important in experiments where spin-dependent effect is small enough. This paper describes two sets of equipments that make spin flip for extracted beams. In both cases, these devices are absolutely distinct, because they are appropriate for different particles and at different energy range. The first of them is intended for future muon (g-2) experiment, which is under preparation now at JPARC. Here, the muon spin flip will be done by the chain of electrostatic and magnetic bends at the kinetic energy of 340 keV. A beam matching is provided by a number of short solenoids. The other flipper (or Siberian Snake) will rotate spin of protons or antiprotons, which come from -meson decay with the energy up to 40 GeV. This experiment (#24) is planed at IHEP, Protvino. In this case, two superconducting helical magnets with opposite helicities and magnetic field 4.5 T will be used. To correct beam trajectory, additional dipole correctors are required.
Capiluppi M., Carassiti V., Ciullo G., Lenisa P., Nass A., Steffens E. Dual HD Cavity for the PAX Target Polarimeter The spin filtering tests with antiprotons proposed to the CERN-SPSC by the PAX Collaboration require that the filter target is operated subsequently with polarized hydrogen and deuterium gas. Therefore, the target polarimeter must enable one to measure both species. A special resonator with both transverse magnetic rf-components relative to the static B-field for the polarimeter's rf-transitions has been developed that can be operated on two adjustable frequencies. The design and successful test of the resonator based on two sets of tilted twin lines is described.
Tvaskis V., Dutta D., Gaskell D., Narayan A. Precise Polarization Measurements via Detection of Compton Scattered Electrons The Qweak experiment at Jefferson Lab aims to make a 4% measurement of the parity-violating asymmetry in elastic scattering at very low Q² of a longitudinally polarized electron beam off a proton target. One of the dominant experimental systematic uncertainties in Qweak will result from determining the beam polarization. A new Compton polarimeter was installed in the fall of 2010 to provide a noninvasive and continuous monitoring of the electron beam polarization in Hall C at Jefferson Lab. The Compton-scattered electrons are detected in four planes of diamond microstrip detectors. We have achieved the design goals of < 1% statistical uncertainty per hour and expect to achieve 1% systematic uncertainty.
Session 7. POLARIZED ION AND LEPTON SOURCES AND TARGETS
Barashkova I.I., Bunyatova E.I., Kravets L.I. Polypropylene Track Membranes as a Promising Material for Targets with Polarized Protons Polypropylene track membranes made by irradiation of polypropylene films with a beam of high-energy heavy ions followed by chemical etching of latent ion tracks are proposed for being used as a polarized target material. To give membranes paramagnetic properties needed for allowing dynamic polarization of nuclei, the nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl was introduced in the samples by the thermal diffusion technique. Using the electron paramagnetic resonance method, we obtained information on paramagnetic centers in the polymer matrix of the membranes and determined the nitroxyl radical concentration and rotational mobility of the spin probe in them.
Gaisser M., Nass A., Strher H. DSMC Simulations of Polarized Atomic Beam Sources Including Magnetic Fields In recent decades a lot of work has been done to understand and optimize the output of polarized atomic beam sources. However, there are many effects which prevent a complete analytic description of the system. Now, a DSMC (Direct Simulation Monte Carlo) simulation based on OpenFOAM 1.7.1 using Birds algorithm is set up. So far, the simulated particles have been given spin, and a generic utility to include arbitrary magnetic fields has been created. The equation of motion in every timestep is solved by a fourth order Runge-Kutta scheme. In this contribution, we describe promising first results of the simulations. Additionally a tool to measure the collision age has been created. Further effects to be included are recombination on the walls and spin exchange collisions. After that an algorithm will be included to optimize the output of the atomic beam source.
Fimushkin V.V., Kovalenko A.D., Kutuzova L.V., Prokofichev Yu.V., Belov A.S., Turbabin A.V., Zubets V.N. Status of the Polarized Ions Source for the JINR Accelerator Complex The project assumes the design and construction of a universal high-intensity source of polarized deuterons (protons) using a charge-exchange plasma ionizer. The output D⁺ (H⁺) current of the source is expected to be at a level of 10 mA. The polarization will be up to 90% of the maximal vector (1) for D⁺ (H⁺) and tensor (+1, -2) for D⁺ polarization. Realization of the project is carried out in close cooperation with INR of the RAS (Moscow). The equipment available from the CIPIOS ion source (IUCF, Bloomington, USA) is partially used for the Dubna setup. The new source at the JINR Nuclotron accelerator facility will make it possible to increase the polarized deuteron beam intensity up to the level of 10¹⁰ d/pulse. The first results of the source of polarized atoms testing are presented.
Maxwell J., Milner R., Epstein C. Development of a Polarized ³He Ion Source for RHIC A polarized ³He ion source is under development for use at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The gas will be polarized using metastability exchange optical pumping, then transferred into the electron beam ion source for ionization. Nuclear polarization of the order of 70% is expected under optimal conditions, and roughly 10¹¹ doubly-ionized ³He⁺⁺ ions will be created in each 20 s pulse.
Pierce J., Maxwell J., Keith C. Dynamically Polarized Target for the g₂^p and G_E^p Experiments at the Jefferson Lab Recently, two experiments were concluded in Hall A at the Jefferson Lab which utilized a newly assembled, solid, polarized hydrogen target. The primary components of the target are a new, high cooling power ⁴He evaporation refrigerator, and a repurposed, superconducting split-coil magnet. It has been used to polarize protons in irradiated NH₃ at a temperature of 1 K and at fields of 2.5 and 5.0 tesla. Maximum polarizations of 55 and 95% were obtained at those fields, respectively. To satisfy the requirements of both experiments, the magnet had to be routinely rotated between angles of 0, 6, and 90 with respect to the incident electron beam.
Gapienko I.V., Plis Yu.A. Density Matrix in Technique of Polarized Ion Sources The use of the density matrix is the most direct way to work with polarization parameters. The solutions of the equation for the density matrix are obtained for hydrogen and deuterium. The magnetic moments of nuclei are explicitly incorporated into the equations, even though numerically it does not make a big difference. It is shown that in the general case, the density matrix cannot be reduced to the one with the only spin variables of the nucleus in contradiction to the statement of K.Blum (Blum K. Density Matrix Theory and Applications).
Zelenski A., Atoian G., Ritter J., Steski D., Podolyako F., Sorokin I., Vizgalov I., Klenov V., Zubets V., Davydenko V., Ivanov A., Kolmogorov A. The RHIC Polarized Source Upgrade The RHIC polarized H^- ion source is being upgraded to higher intensity and polarization for the use in the RHIC polarization physics program at enhanced luminosity RHIC operation. The higher beam intensity will allow reduction of the longitudinal transverse beam emittance at injection to AGS to reduce polarization losses in AGS. There is also a planned RHIC luminosity upgrade by using the electron beam lens to compensate the beam-beam interaction at collision points. This upgrade is also essential for future BNL plans for a high-luminosity electron-proton (ion) Collider eRHIC. The basic limitations on the high-intensity H^- ion beam production in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapor jet ionizer cell were experimentally studied.
Session 8. FUTURE FACILITIES AND EXPERIMENTS
Avakian H. Studies of the 3D Structure of the Proton at JLab In recent years, parton distributions, describing longitudinal momentum, helicity and transversity distributions of quarks and gluons, have been generalized to account also for transverse degrees of freedom. Two new sets of more general distributions, Transverse Momentum Distributions (TMDs) and Generalized Parton Distributions (GPDs), were introduced to describe transverse momentum and spatial distributions of partons. Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs) in semi-inclusive and hard exclusive processes, providing access to TMDs and GPDs, respectively. Studies of TMDs and GPDs are also among the main driving forces of the JLab 12 GeV upgrade project.
Dalton M.M. (Hall A Collab.) Recent Results and Future Direction of the Parity-Violating Electron Scattering Program in Hall A at Jefferson Lab Hall A at Jefferson Lab has recently completed three experiments done using the technique of parity-violating electron scattering. Taken together these experiments are a good demonstration of the versatility of this approach. Looking forward, there are two very large scale parity-violation experiments approved to run in Hall A in the 12 GeV era. These experiments represent a significant increase in precision and technical requirements.
Giordano F. (PHENIX Collab.) A New Forward Spectrometer for PHENIX In the last decade PHENIX has accessed via longitudinal double spin asymmetries the gluon helicity inside the proton, started probing flavor-dependent valence and sea quark helicity distributions and started to explore the proton transverse spin structure. A major upgrade is planned for the next decade that will provide an increased acceptance and additional tracking and electromagnetic plus hadronic calorimetry in the forward region. Here, the layout of the new forward detector system will be discussed, together with the new insights in the proton spin structure that the new forward PHENIX spectrometer will provide.
Kondratenko A.M., Derbenev Ya.S., Filatov Yu.N., Lin F., Morozov V.S., Kondratenko M.A., Zhang Y. Preservation and Control of the Proton and Deuteron Polarizations in the Proposed Electron-Ion Collider at Jefferson Lab We propose a scheme of preserving the proton and deuteron beam polarizations during acceleration and storage in the proposed electron-ion collider at Jefferson Lab. This scheme allows one to provide both the longitudinal and transverse polarization orientations of the proton and deuteron beams at the interaction points of the figure-8 ion collider ring. We discuss questions of matching the polarization direction at all stages of the beam transport including the prebooster, large booster and ion collider ring.
Kovalenko A.D., Filatov Yu.N., Kondratenko A.M., Kondratenko M.A., Mikhaylov V.A. Polarized Deuterons and Protons at NICA @ JINR The novel scheme of proton and deuteron polarization control in the NICA collider at Dubna is proposed. By means of two Siberian Snakes with solenoid magnetic field the beam spin tune is shifted to the «zero» spin resonance vicinity, whereas manipulation of the polarization is realized by «weak» field solenoids. The scheme makes it possible to obtain any desired direction of the polarization in the both MPD and SPD detectors for any sort of the particles. The possibility of the beam polarization control in the orbit plane at any azimuth of the collider magnetic arcs exists also. The last gives necessary flexibility of optimal matching the beam polarization at injection into collider and at the polarimetery monitor points.
Ladygin V.P., Uesaka T., Glagolev V.V., Gurchin Yu.V., Isupov A.Yu., Itoh K., Janek M., Karachuk J.-T., Kawabata T., Khrenov A.N., Kiselev A.S., Krasnov V.A., Kurepin A.B., Kurilkin A.K., Kurilkin P.K., Ladygina N.B., Lipchinski D., Maeda Y., Malakhov A.I., Martinska G., Nedev S., Piyadin S.M., Popovichi J., Rangelov S., Reznikov S.G., Rukoyatkin P.A., Sakaguchi S., Sakai H., Sekiguchi K., Shikhalev M.A., Suda K., Terekhin A. A., Trpisova B., Urban J., Vasiliev T.A., Vnukov I.E., Witala H. Spin Physics in Few Body Systems at Nuclotron The review of the recent results on spin effects in few nucleon systems obtained at LHEP, JINR, are presented. The data on the deuteron analyzing powers in different reactions in the wide energy range demonstrate the sensitivity to the spin structure of the light nuclei. The future plans on the studies with polarized deuterons from new polarized ion source at Nuclotron will be reported.
Balandin V.P., Baskakov A.E., Basilev S.N., Brash E., Bushuev Yu.P., Gavrishchuk O.P., Glagolev V.V., Jones M.K., Kadykov M.G., Khandaker M., Kirillov D.A., Kiryushin Yu.T., Kostyukhov E.V., Kuzmin N.A., Livanov A.N., Manyakov P.K., Martinska G., Meziane M., Movchan S.A., Muinsky J., Pentchev L., Perdrisat C.F., Piskunov N.M., Povtoreiko A.A., Punjabi V., Rukoyatkin P.A., Shindin R.A., Shutov A.V., Shutova N.A., Sitnik I.M., Slepnev V.M., Slepnev I.V., Sychkov S.Ya., Tomasi-Gustafsson E., Vasiliev S.E., Vishnevsky A.V., Yukaev A.I., Urban J., Wojtsekhowski B. Measurement of Analyzing Power for the Reaction + CH₂ at Polarized Proton Momentum of 7.5 GeV/c (ALPOM2 Proposal) An accurate data base for the analyzing power of thick CH₂ analyzers for high energy protons has been at the basis of several research efforts in a number of laboratories. Starting in the late eighties such data were collected at SATURNE in Saclay, and with the Synchrophasotron in Dubna, and led to an extensive program of study of polarization phenomena in pd interaction, either backward elastic scattering or breakup [1-6]. At about the same time it became evident that measuring polarization observables in elastic ep was going to be the best approach to determine the form factors of the proton, G_Ep and G_Mp, as had been predicted by Akhiezer and Rekalo [7].
Quaresma M. (COMPASS Collab.) Polarised Drell-Yan Measurements at COMPASS-II The spin structure of the nucleon and its Parton Distribution Functions (PDFs) are important topics studied by the COMPASS experiment at CERN. So far, the transverse momentum dependent PDFs (TMD PDFs) of the proton and deuteron have been studied in Semi-Inclusive Deep Inelastic Scattering (SIDIS). The Drell-Yan (DY) process is a complementary way to access the TMD PDFs, using a transversely polarised target. Studying the angular distributions of dimuons from the DY events produced in the collisions of a ^- beam with 190 GeV/c momentum off a transversely polarised proton target (NH₃), we are able to extract the azimuthal spin asymmetries, which are generated by 4 out of the 8 TMD PDFs needed to describe the nucleon structure at leading order QCD. The expected sign change in Sivers and Boer-Mulders functions when accessed from DY and SIDIS will be checked [1]. The opportunity to study, in the same experiment, the TMD PDFs from both SIDIS and DY processes is unique at COMPASS. The COMPASS-II Proposal [2] was approved by CERN including one year for polarised DY measurements; the beginning of the DY data taking is scheduled for 2014. The feasibility of the measurement was proven by several beam tests performed so far.
Rakotozafindrabe A., Anselmino M., Arnaldi R., Brodsky S.J., Chambert V., Didelez J.P., Genolini B., Ferreiro E.G., Fleuret F., Hadjidakis C., Lansberg J.P., Lorc C., Rosier P., Schienbein I., Scomparin E., Uggerhj U.I. Spin Physics at a Fixed-Target Experiment at the LHC (AFTER@LHC) We outline the opportunities for spin physics which are offered by a next generation and multipurpose fixed-target experiment exploiting the proton LHC beam extracted by a bent crystal. In particular, we focus on the study of single transverse spin asymmetries with the polarisation of the target.
Shestakov Yu.V., Barkov L.M., Dmitriev V.F., Golovin R.A., Kudryavtsev V.N., Lazarenko B.A., Mishnev S.I., Nikolenko D.M., Rachek I.A., Sadykov R.Sh., Stibunov V.N., Toporkov D.K., Shekhtman L.I., Zevakov S.A. Tagging System for Almost-Real Photons at VEPP-3 Storage Ring At BINP the construction of the tagging system for almost-real photons (TS) is in progress. The energy of tagging photons can be up to 1.5 GeV. The projected energy resolution of TS is better than 1%. For at least a half of photons the linear polarization can be determined. The tagging system will extend the possibilities for photoreaction studying at VEPP-3 significantly. TS would allow one to perform a complete kinematics reconstruction, thus permitting a reliable rejection of the background processes; to extend the measurements to higher photon energy; to enable -asymmetry measurements and double-polarization experiments.
Session 9. MEDICAL AND TECHNOLOGICAL APPLICATIONS OF SPIN PHYSICS
Engels R., Grigoryev K., Kochenda L., Kravtsov P., Mikirtytchiants M., Rathmann F., Paetz gen., Schieck H., Strher H., Trofimov V., Vasilyev A., Vznuzdaev M. Polarized Fusion Since more than 50 years, it has been discussed the problem of increasing the gain of nuclear fusion reactors with the use of polarized fuel. For example, the total cross sections of the fusion reactions d + t ⁴He + n or ³He + d ⁴He + p are increased by a factor of about 1.5 if the spins of both incoming particles are aligned. But before the polarized fuel can be used for energy production in the different types of reactors, a number of questions must be answered. In this contribution we give an overview on our various activities in this field of research.
Kiselev Yu. Blood Analysis for Early Cancer Detection The interaction between the nuclear quadrupole moments of ions and the electric field gradient in a biological membrane can explain the mechanism of active transport in cells. On the basis of a model, we discuss the NMR isotopic analyzer of blood for the detection of cancer without exposing the patient to any radiation. The method involves a low temperature technique.
Strzik-Kotlorz D. Magnetic Resonance Spectroscopy of the Human Brain A brief description of the magnetic resonance spectroscopy (MRS) in the human brain examinations is given. MRS allows a noninvasive chemical analysis of the brain using a standard high field MR system. Nowadays, the dominant form of MR brain spectroscopy is proton spectroscopy. Two main techniques of MRS, which utilize the chemical shift of metabolites in the external magnetic field, are SVS (single voxel) and CSI (single slice). The major peaks in the spectrum of a normal brain include NAA, Cr, Cho and m-Ins, which are neuronal, energetic, membrane turnover and glial markers, respectively. In disease, two pathological metabolites can be found in the brain spectra: Lac, which is the end product of anaerobic glycolysis and Lip, which is a marker of membrane breakdown, occurring in necrosis. The common way to analyze clinical spectra is to determine metabolite ratios, e.g., NAA/Cr, Cho/Cr, Cho/NAA. This analysis permits a safe and noninvasive examination of the brain tissue, as each disease state has its own characteristic spectroscopic image. MRS is a valuable diagnostic tool in such clinical applications as detecting brain tumors and differentiating tumors from inflammatory and infectious processes. Proton MRS is also very helpful in diagnostic of ischemic lesions, Alzheimer's disease and hepatic encephalopathy. The MRS brain spectra should always be correlated with the Magnetic Resonance Imaging (MRI) results and alone cannot make neurological diagnosis.
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Saha B. Isotropic and Anisotropic Dark Energy Models (eng, 970 Kb) The evolution of the Universe filled with dark energy (DE) with or without perfect fluid is discussed. In doing so, we consider a number of cosmological models, namely Bianchi type I, III, V, VI₀, VI, and FRW one. For the anisotropic cosmological models we have used proportionality condition as an additional constraint. The exact solutions to the field equations in quadrature are found in the case of a BVI model. It was found that the proportionality condition used here imposed severe restriction on the energy-momentum tensor, namely, it leads to isotropic distribution of matter. Anisotropic BVI₀, BV, BIII, and BI DE models with variable EoS parameter have been investigated by using a law of variation for the Hubble parameter. In this case the matter distribution remains anisotropic, though, depending on the concrete model, there appear different restrictions on the components of energy-momentum tensor. That is why we need an extra assumption such as a variational law for the Hubble parameter. It is observed that, at the early stage, the EoS parameter is positive, i.e., the Universe was matter-dominated at the early stage but at later time the Universe is evolving with negative values, i.e., the present epoch. DE model presents the dynamics of EoS parameter whose range is in good agreement with the acceptable range by the recent observations. A spatially homogeneous and anisotropic locally rotationally symmetric Bianchi-I space-time filled with perfect fluid and anisotropic DE possessing dynamical energy density is studied. In the derived model, the EoS parameter of DE (^(de)) is obtained as time varying and it is evolving with negative sign which may be attributed to the current accelerated expansion of Universe. The distance modulus curve of derived model is in good agreement with SNLS type Ia supernovae for high red-shift value which in turn implies that the derived model is physically realistic. A system of two fluids within the scope of a spatially flat and isotropic FRW model is studied. The role of the two fluids, either minimally or directly coupled in the evolution of the dark energy parameter, has been investigated. In doing so, we have used three different ansatzs regarding the scale factor that gives rise to a variable decelerating parameter. It is observed that, in the noninteracting case, both the open and the flat Universes can cross the phantom region whereas in the interacting case only the open Universe can cross the phantom region. The stability and acceptability of the obtained solution are also investigated.
Ternov A.I., Eminov P.A. Massive Neutrino Radiative Decay in an Intense External Magnetic Field and in Medium (rus, 303 Kb) A review of the current status of the theory of massive neutrino radiative decay is presented. We further develop our previous studies and perform the detailed analysis of the process of radiative decay of a massive Dirac neutrino in an intense external magnetic field H H₀ = m_e²c³/e = 4.41 10¹³ G in the presence of medium (a degenerate electron gas). The probability of the above-mentioned process is calculated. It is found out that the presence of a dense medium essentially increases the rate of decay as compared to the rate of decay in magnetic field, both in cases of relativistic and nonrelativistic neutrinos. Possible astrophysical applications of the obtained results are considered.
Papash A.I., Smirnov A.V., Welsch C.P. Beam Dynamics in an Ultralow Energy Storage Rings (Review of Existing Facilities and Feasibility Studies for Future Experiments) (eng, 2.4 Мb) Storage rings operating at ultralow energies and, in particular, electrostatic storage rings have proven to be invaluable tools for atomic and molecular physics. Due to the mass independence of the electrostatic rigidity, these machines are able to store a wide range of different particles, from light ions to heavy singly charged biomolecules. However, earlier measurements showed strong limitations on beam intensity, fast decay of ion current, reduced lifetime, etc. The nature of these effects was not fully understood. Also a large variety of experiments in future generation ultralow energy storage and decelerator facilities including in-ring collision studies with a reaction microscope require a comprehensive investigation of the physical processes involved into the operation of such rings. In this paper, we present review of nonlinear and long-term beam-dynamics studies on example of the ELISA, AD Recycler, TSR and USR rings using the computer codes BETACOOL, OPERA-3D and MAD-X. The results from simulations were benchmarked against experimental data of beam losses in the ELISA storage ring. We showed that decay of beam intensity in ultralow energy rings is mainly caused by ion losses on ring aperture due to multiple scattering on residual gas. Beam is lost on ring aperture due to small ring acceptance. Rate of beam losses increases at high intensities because the intrabeam scattering effect adds to vacuum losses. Detailed investigations into the ion kinetics under consideration of the effects from electron cooling and multiple scattering of the beam on a supersonic gas jet target have been carried out as well. The lifetime, equilibrium momentum spread and equilibrium lateral spread during collisions with this internal gas jet target were estimated. In addition, the results from experiments at the TSR ring, where low-intensity beam of CF⁺ ions at 93 keV/nucl. has been shrunk to extremely small dimensions have been reproduced. Based on these simulations, conditions for stable ring operation with extremely low-emittance beam are presented. Finally, results from studies into the interaction of ions with a gas jet target at 3-30 keV energy range are summarized.
Meshkov I.N. Barrier Bucket Method in Cyclic Accelerators (rus, 602 Кb) The main principles of the Barrier Bucket Method of charge particles stacking and acceleration in proton synchrotrons are described. The consideration is done with two models of «rectangular barriers» and «quasi-sinusoidal» ones using different approaches to analysis of particle motion. The first of them - so-called «step by step approach», allows us to give a very clear physical explanation of the method and obtain easily the main characteristics of the method in analytical form. However, that is not always an efficient way. Therefore, the general case of the «barriers» of an arbitrary form is considered as well and differential equations of particle phase motion are derived. This approach gives ample opportunities for analysis and numerical simulations of different phase dynamics regimes of particles in cyclic accelerators. Numerical examples for the method illustration are presented.
Zhabitsky V.M. Beam Dynamics in Synchrotrons with Digital Wideband Transverse Feedback Systems (rus, 1.5 Мb) A review of modern studies of beam dynamics in synchrotrons with digital wideband transverse feedback systems is presented. Features of decisions for decrements and frequency shifts of the coherent betatron oscillation decay caused by a digital signal processing in a feedback chain are revealed. Theoretical predictions are compared with the experimental data obtained at the Large Hadron Collider.
Zabaev V.N., Kaplin V.V., Kuznetsov S.I., Uglov S.R. An Overview of Investigation of X-ray Transition Radiation of Electrons with Energy 300-900 MeV in Periodical Multifoil Radiators (rus, 336 Кb) An overview of the results of experimental studies at the Tomsk synchrotron of the resonant X-ray transition radiation generated by relativistic electrons in periodic multifoil radiators is presented. The experiments were made with the use of both the internal beam of the Tomsk synchrotron and the external beam of secondary electrons of a magnetic pair -spectrometer in the range of electron energy of 300-900 MeV. The multifoil radiators consist of the sets of thin amorphous foils of different materials. The generation of X-rays in a compound radiator consisting of the multifoil radiator and a crystal was also investigated. In this case, the resonant X-ray transition radiation generated in the multifoil radiator was then diffracted in the crystal and emitted at Bragg angles together with parametric X-ray radiation generated in the crystal. The spectral and angular properties of the resonant X-ray transition radiation and of the diffracted resonant X-ray transition radiation were investigated. The ratio of the contributions of the diffracted resonant X-ray transition radiation and of other types of radiation in the total flux of coherent X-rays generated by electrons in multifoil radiators and crystals was also estimated.
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Chizhov M.V., Boyko I.R., Bednyakov V.A., Budagov J.A. Hadron Collider Potential for Excited Bosons Search (eng, 387 Kb) The e⁺e^- and ⁺⁺ dilepton final states are the most clear channels for a new heavy neutral resonance search. Their advantage is that usually in the region of expected heavy-mass resonance peak the main irreducible background, from the Standard Model Drell-Yan process, contributes two orders of magnitude smaller than the signal. In this paper, we consider the future prospects for search for the excited neutral Z* bosons. The bosons can be observed as a Breit-Wigner resonance peak in the dilepton invariant mass distributions in the same way as the well-known extra gauge Z' bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow one to distinguish them from the other heavy neutral resonances. At present, only the ATLAS Collaboration has looked for such new excitations at the Large Hadron Collider and has published its results for 7 TeV collision energy. After successful comparison of our evaluation with these official results, we present our estimations for the discovery potential and the exclusion limits on the Z-boson search in pp collisions at higher centre-of-mass energies and different luminosities. In particular, LHC Run 2 can discover Z boson with its mass up to 5.3 TeV, while the High Luminosity LHC can extend that reach to 6.2 TeV. The High Energy LHC (with collision energy of 33 TeV) will be able to probe two times heavier resonance masses at the same integrated luminosities.
Akhundov A.A., Arbuzov A.B., Riemann S., Riemann T. The ZFITTER Project (eng, 387 Kb) The ZFITTER project is aimed at the computation of high-precision theoretical predictions for various observables in high-energy electron-positron annihilation and other processes. The stages of the project development are described. The emphasis is made on applications to the analysis of LEP data. The present status of the project and perspectives are given as well.
Malkovich E.G. Noncompact Riemannian Spaces with G₂, Spin(7) and SU(2m) Holonomies (rus, 310 Kb) The survey contains a description of the author's results on constructing Riemannian metrics with exceptional holonomies on noncompact manifolds. We give detailed description of how to reduce a condition of the holonomy to be exceptional to a system of ODE. We describe a behavior of the trajectories and the ways to resolve singularities of such systems, concrete examples were studied. Introduction and Sec.1 contain necessary definitions and well-known facts about holonomies. Conclusion contains a description of other results proved with help of the same technique and a minimal survey on Lorentzian holonomies.
Kuksa V.I. Unstable States in Quantum Theory (rus, 685 Kb) A review of the different approaches in the description of the unstable particles is presented. The main problems and their treatments have been considered which arise in the quantum-field description of these particles. The approach is picked out which is based on smeared (continual) mass conception following from the finite lifetime of unstable particles. Quantum-field model of unstable particles is presented in detail which is built on the base of two basic elements with axiomatic status. Within the frame of the model, the main processes (decay and scattering) with participation of unstable particles are considered and the formalism describing physical characteristics of these processes is developed. The model was successfully applied to the description of the pair and triple boson production at the linear collider, top-pair production and some hadron decay processes. The factorization method was developed on the base of the model approach which simplifies significantly the description of the complicated chain processes of the scattering and decay with the participation of unstable particles.
Kolomietz V.M. Memory Effects in Nuclear Fermi Liquid (rus, 325 Kb) The kinetic theory is applied to the nuclear Fermi liquid. The nuclear collective dynamics is treated in terms of the observable variables: particle density, current density, pressure, etc. The influence of Fermi-surface distortion, relaxation processes and memory effects on the nuclear dynamics is studied. We show that the presence of the dynamic Fermi-surface distortion gives rise to some important consequences in the nuclear dynamics which are absent in classical liquids. We discuss the nuclear small amplitude excitations, the spinodal instability, the nuclear fission and the bubble instability in heated Fermi liquid in the presence of the memory effects.
Kobzev A.P. About the Radiation Mechanism of a Uniformly Moving Charge (rus, 351 Kb) The radiation mechanism of a uniformly moving charge is discussed in detail with attention to the description of the Vavilov-Cherenkov and transition radiation effects. A well-grounded proof is given that this mechanism is incorrect because it is in conflict with the energy and momentum conservation laws and Newton's first law. A lucid explanation of the mechanism for the Vavilov-Cherenkov radiation and the transition radiation is suggested by considering the atomic structure of solids, which does not require violation of fundamental laws. It is shown that the Vavilov-Cherenkov radiation and the transition radiation are emitted by the atoms of the medium that are polarized by the moving particle, rather than by the particle itself moving through a medium. It is obvious that in this case neither the anomalous nor the normal Doppler effect is possible in the process of the Vavilov-Cherenkov radiation emission. It is shown that the Vavilov-Cherenkov radiation and the transition radiation cannot be emitted at frequencies higher than the inner shell frequency of the atom of the medium. Mistakes caused by using the radiation mechanism of a uniformly moving charge for describing the interaction of a moving charge with a solid are discussed.
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Editorial (eng, 26 Kb)
Berwein M., Brambilla N., Vairo A. Renormalization of Loop Functions in QCD (eng, 180 Kb) We give a short overview of the renormalization properties of rectangular Wilson loops, the Polyakov loop correlator, and the cyclic Wilson loop. We then discuss how to renormalize loops with more than one intersection, using the simplest nontrivial case as an illustrative example. Our findings expand on previous treatments. The generalized exponentiation theorem is applied to the Polyakov loop correlator and is used to renormalize linear divergences in the cyclic Wilson loop.
Cherednikov I.O. On Path Dependence of the QCD Correlation Functions (eng, 290 Kb) Gauge-invariant hadronic and vacuum correlation functions in QCD contain the systems of Wilson lines and loops having complicated geometrical structure. Path dependence propagates, therefore, into such important properties of the quantum correlators as the renormalization-group behaviour, light-cone peculiarities, evolution, etc. In the present paper, I briefly overview several instructive examples of the manifestations of the structure of paths in the hadronic and vacuum correlation functions with explicit transverse momentum/distance dependence. In particular, the transverse-momentum-dependent (TMD) parton densities and the skewed jet quenching parameter in Euclidean and Minkowski space-time are addressed.
D'Alesio U., Murgia F., Pisano C. Collins and Sivers Effects in jet X: Universality and Process Dependence (eng, 525 Kb) In this paper, we briefly review the transverse-momentum-dependent generalized parton model and its application to the study of azimuthal asymmetries in the distribution of leading hadrons (mainly pions) inside large transverse momentum jets inclusively produced in polarized proton-proton collisions. We put particular emphasis on the phenomenological interest of these observables, in combination with similar asymmetries measured in semi-inclusive deeply inelastic scattering, Drell-Yan processes and e⁺e^- collisions, for the study of the universality properties of the transverse-momentum-dependent parton distribution and fragmentation functions. We present results for RHIC kinematics at center-of-mass energies = 200 and 500 GeV, for central and mainly forward jet rapidities, in particular for the Sivers distribution and the Collins fragmentation function, that are believed to be responsible for many of the largest asymmetries measured in the last years. We also briefly discuss the case of inclusive jet production and recent phenomenological applications of other theoretical approaches, like the colour gauge-invariant generalized parton model and the collinear twist-three approach, aiming at clarifying the issues of the universality and process dependence of transverse-momentum-dependent functions.
Dorn H., Mnkler H., Spielvogel C. Conformal Geometry of Null Hexagons for Wilson Loops and Scattering Amplitudes (eng, 712 Kb) The cross-ratios do not uniquely fix the class of conformally equivalent configurations of null polygons. In view of applications to the Wilson loops and scattering amplitudes, we characterize all conformal classes of null hexagon configurations belonging to given points in cross-ratio space. At first, this is done for the ordered set of vertices. Including the edges, we then investigate the equivalence classes under conformal transformations for null hexagons. This is done both for the set of null hexagons closed in finite domains of the Minkowski space and for the set including those closed via infinity.
Jian-Hua Gao Singularities, Boundary Conditions and Gauge Link in the Light-Cone Gauge (eng, 223 Kb) In this work, we first review the issues on the singularities and the boundary conditions in the light-cone gauge and how to regularize them properly. Then, we will further review how these singularities and the boundary conditions can result in the gauge link at the infinity in the light-cone direction in the Drell-Yan process. Except for reviewing, we also have verified that the gauge link at the light-cone infinity has no dependence on the path not only for the Abelian field, but also for non-Abelian gauge field.
Kidonakis N. NNLL Threshold Resummation for Top-Pair and Single-Top Production (eng, 465 Kb) I discuss threshold resummation at NNLL accuracy in the standard moment-space approach in perturbative QCD for top-pair and single-top production. For top-quark pair production, I present new approximate NNLO results for the total cross section and for the top-quark transverse momentum and rapidity distributions at 8 TeV LHC energy. I discuss the accuracy of the soft-gluon approximation and show that the NLO and NNLO approximate results from resummation are practically indistinguishable from exact NLO and partial NNLO results. For single-top production I present new approximate NNLO results for the total cross sections in all three channels at the LHC and also for the top-quark transverse momentum distributions in t-channel production and in top-quark associated production with a W boson. For both t and single-top production, the agreement of theoretical results with LHC and Tevatron data is excellent.
Kumeriki K., Mller D., Murray M. HERMES Impact for the Access of Compton Form Factors (eng, 881 Kb) We utilize the DVCS asymmetry measurements of the HERMES Collaboration for access to Compton form factors in the deeply virtual regime and to generalized parton distributions. In particular, the (almost) complete measurement of DVCS observables allows us to map various asymmetries into the space of Compton form factors, where we still rely in this analysis on dominance of twist-two associated Compton form factors. We compare this one-to-one map with local Compton form factor fits and a model-dependent global fit.
Hsiang-nan Li Resummation with Wilson Lines off the Light Cone (eng, 487 Kb) I review the resummation formalism for organizing large logarithms in perturbative expansion of collinear subprocesses through the variation of Wilson lines off the light cone. A master equation is derived, which involves the evolution kernel resulting from this variation. It is then demonstrated that all the known single- and double-logarithm summations for a parton distribution function or a transverse-momentum-dependent parton distribution can be reproduced from the master equation by applying appropriate soft-gluon approximations to the evolution kernel. Moreover, jet substructures, information of which is crucial for particle identification at the Large Hadron Collider and usually acquired from event generators, can also be calculated in this formalism.
Makeenko Yu. Scattering Amplitudes of QCD String in the Worldline Formalism (eng, 327 Kb) The derivation of large-N QCD meson-scattering amplitudes in the Regge regime, where the effective theory of long strings is applied in d = 4, is reviewed. A special attention is paid to the reparameterization path integral which plays a crucial role in the consistency of off-shell amplitudes. I show how the linear Reggeon trajectory is obtained for QCD string in the mean-field approximation, which turns out to be exact for the Nambu-Goto string, and discuss the interrelation with perturbative QCD.
Sazdjian H. Gauge-Invariant Quark Green's Functions with Polygonal Wilson Lines (eng, 173 Kb) Properties of gauge-invariant two-point quark Green's functions, defined with polygonal Wilson lines, are studied. Green's functions can be classified according to the number of straight line segments their polygonal lines contain. Functional relations are established between Green's functions with different numbers of segments on the polygonal lines. An integrodifferential equation is obtained for Green's function with one straight line segment, in which the kernels are represented by a series of Wilson loop vacuum averages along polygonal contours with an increasing number of segments and functional derivatives on them. The equation is exactly solved in the case of two-dimensional QCD in the large-N_c limit. The spectral properties of Green's function are displayed.
Chachamis G., Hentschinski M., Madrigal Martnez J.D., Sabio Vera A. Forward Jet Production & Quantum Corrections to the Gluon Regge Trajectory from Lipatov's High-Energy Effective Action (eng, 457 Kb) We review Lipatov's high-energy effective action and show that it is a useful computational tool to calculate scattering amplitudes in (quasi-)multi-Regge kinematics. We explain in some detail our recent work where a novel regularization and subtraction procedure has been proposed that allows one to extend the use of this effective action beyond tree level. Two examples are calculated at next-to-leading order: forward jet vertices and the gluon Regge trajectory.
Vladimirov A.A., Diakonov D. Diffeomorphism-Invariant Lattice Actions (eng, 194 Kb) We present a lattice-discretization procedure which is based on the simplicial lattice and preserves diffeomorphism invariance. The presented procedure is the straightforward generalization for the procedure used for discretization of the spinor gravity [7]. As a stable way to guarantee the removing of the lattice regularization, i.e., the continuum limit, for lattice diffeomorphism-invariant theories, we propose to tune the system to the point of phase transition. We expect that the Einstein gravitation is achieved at this point.
Fan Wang, Sun W.M., Chen X.S., Zhang P.M. Problems Related to Gauge Invariance and Momentum, Spin Decomposition in Nucleon Structure Study (eng, 212 Kb) How do the quark and gluon share the nucleon momentum? How does the nucleon spin distribute among its constituents? What do the quark and gluon momentum, spin and orbital angular momentum mean? These problems are analyzed and a solution is proposed based on gauge invariance principle, canonical quantization rule and Poincar covariance.
Synopsis (rus, 69 Kb)
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Part 5-6	up
In memory of V. G. Kadyshevsky (rus, 165 Кb)
Tsyganov Yu.S. Synthesis of New Superheavy Elements at the Dubna Gas Filled Recoil Separator: Sum of Technologies (rus, 2 Мb) All new superheavy element isotopes in ⁴⁸Ca induced reactions and with actinide targets were synthesized at the Dubna Gas Filled Recoil Separator (DGFRS, GNS). The success was achieved due to application of specific algorithms, instruments and methods with record parameters for that area, especially, detecting techniques, measurements of effective equilibrium charge states of heavy ions passing through a low pressure hydrogen, statistical approaches to estimate random parameters of multichain events, beamless methods to test electronic modules and some others. The author analyses approaches which finally lead to evident success in experiments aimed at the synthesis of superheavy nuclei. Ways to develop the detecting systems are considered by the author too. In part, those facilities like TASCA, SHIP and GARIS (RIKEN) are within the scope of the author's interest. -particle detection methods used before the DGFRS application are also considered in brief. More than twenty years in the DGFRS application methods, algorithms, and constructions are presented.
Adamian G.G., Antonenko N.V., Zubov A.S. Dinuclear Systems in Complete Fusion Reactions (rus, 1.8 Мb) Formation and evolution of dinuclear systems in the complete fusion reactions is considered. On the basis of the dinuclear system concept, the process of formation of a compound nucleus is studied. The arguments, validating this concept, are adduced. The main problems of the description of complete fusion in the adiabatic approach are listed. Calculations of the evaporation residue cross sections in the complete fusion reactions, leading to the formation of the superheavy nuclei, are shown. Isotopic trends of the heavy nuclei formation cross sections are considered in the complete fusion reactions.
Naghdi M. Nucleon-Nucleon Interaction: A Typical/Concise Review (eng, 823 Kb) Nearly a recent century of work is devoted to Nucleon-Nucleon (NN) interaction issue. We review some overall perspectives of NN interaction with a brief discussion about deuteron, general structure, and symmetries of NN Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN-interaction models, as frameworks to build NN potentials, are reviewed concisely. We try to include and study almost all well-known potentials in a similar way, discuss more on various commonly used plain forms for two-nucleon interaction with an emphasis on the phenomenological and meson-exchange potentials as well as the constituent-quark potentials and new ones based on chiral effective field theory and working in coordinate space mostly. The potentials are constructed in a way that fits NN-scattering data, phase shifts, and are also compared in this way usually. An extra goal of this study is to start comparing various potential forms in a unified manner. So, we also comment on the advantages and disadvantages of the models and potentials partly with reference to some relevant works and probable future studies.
Dovbnya A.N., Kuplennikov E.L., Kandybey S.S., Krasiljnikov V.V. Neutrons against Cancer (rus, 442 Кb) The review is dedicated to analysis and generalization of researches carried out during the last few decades in industrially advanced countries to use fast, epithermal and thermal neutrons for therapy of malignant tumours. Basic facilities for neutron production used for cancer treatment are presented. Optimal parameters of therapeutic beams are described. Methods of using neutrons with different energy regions are discussed. Results and medical treatment efficiency are given. The comparison of the current state of neutron therapy of tumors and alternative treatments with beams of protons and carbon ions is conducted. Main attention is given to possibility of practical use of accumulated experience of neutron beams application for therapy of cancer.
Bednyakov A.A. On Moliere's Theory of Multiple Scattering of Fast Charged Particles (1947-1948) and Its Critique during the Next Years (rus, 1.2 Мb) Some misunderstandings concerning the theory of multiple scattering of fast charged particles in the matter, developed by Moliere in 1947-1948, and its application to experimental data analysis are discussed in the paper. It is demonstrated that criticism of this theory afterwards is based on a wrong interpretation of Moliere's method of definition of the scattering cross section on atom, when screening of its nuclear field by orbital electrons can be described by the Thomas-Fermi statistical model. The accurate usage of the original method of Moliere demonstrates that Moliere's cross section is in a general accordance with the results of the latest «classical» calculations of Lindhard with co-workers and with those by other authors.
Potylitsyn A.P., Kolchuzhkin A.M. Statistical Simulation of the Multiple Compton Scattering Process (rus, 394 Кb) A few laboratories are developing monochromatic sources of X-rays and gamma quanta based on Compton backscattering (CBS) process of laser photons by relativistic electrons. The modern technologies can provide such a photon concentration in the interaction point where each electron can emit a few hard photons. In contrast with the well-known nonlinear CBS process where an initial electron «absorbs» a few laser photons and emits one hard photon, the above-mentioned process may be named as multiple CBS process and can be characterized by a mean number of emitted photons. In this paper we developed an approach based on Monte Carlo technique allowing us to simulate spectral distributions of photons emitted into a narrow collimator for linear CBS process and for nonlinear one with taking into account multiplicity of collisions and showed that monochromaticity of radiation is worsening due to multiple CBS process. For design and construction of new CBS sources there should be foreseen such an effect.
Altaisky M.V., Kaputkina N.E., Krylov V.A. Quantum Neural Networks: Current State and Perspectives of Development (rus, 1.1 Мb) The idea of quantum neural network first presented in [34] is a conjunction of the concept of artificial neural network and that of quantum computation. The first systematic study of artificial quantum neural networks was presented in T.Menner Ph.D. Thesis (1998). The works of Menner and Narayanan [42,43], Kouda, Matsui and Nishimura [35,36], Altaisky, Zhou and others [2,68,67] have laid the basis for the quantum-inspired learning algorithms, which are now in use in different teaching programs and computer games [29,30]. The first scalable model of artificial quantum neural network suitable for practical applications has been implemented by D-Wave Systems Inc. [33]. It is a quantum Hopfield network implemented on superconducting quantum interference devices (SQUID). In present paper, we analyze the principles and possibilities of alternative implementation of quantum neural network on the basis of quantum dots and quantum wires. The prospectives of application of quantum neural networks to automatic control, associative memory devices, and simulation of biological and social networks are considered.
Ahmadov A.I., Kuraev E.A. Jets Production in Peripheral Interactions of High-Energy Leptons, Quarks, Photons, and Gluons with the Proton (eng, 372 Кb) The paper presents short historical reviews of the processes of lepton-pairs production in peripheral interaction of leptons and ions at high energies. The orders of magnitude of the QED and QCD cross sections with the production of two and three jets are given. The technique of the analysis is described in detail based on the parameterization of Sudakov 4-momentum tasks and writing the amplitude in an explicit gauge-invariant form. Based on this formalism, the differential cross sections of the QCD processes p ()p; qp (qQ)p; p (Q)p were obtained, including the distribution on transverse momentum component of jets fragments. It was shown that the role of the contribution of «non-Abelian» nature may become dominant in a particular kinematics of the final particles. The kinematics, in which the initial particle changes the direction of motion to the opposite one, was considered in the case of heavy quark-antiquark pair production. In the appendices, the details of the calculations and the explicit form of the differential cross sections are given. Some extended comments on the frequently used cross sections of the pair production in the case of two-photon scattering are presented. In particular, the degree of the longitudinal polarization of the positron, at the interaction of polarized initial electron, was calculated. The method of calculating the cross sections of the 2 2 processes in QCD, based on the isolation of irreducible color structures, and the method CALCUL of spiral amplitudes were discussed in detail.
Synopsis (rus, 62 Kb)
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