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GENERAL CONSTRAINTS ON SPIN OBSERVABLES;
APPLICATIONS TO `p+p 
` L+L AND TO POLARIZED QUARK DISTRIBUTIONS
Artru X., Richard J.-M.
The density matrix formalism and the positivity conditions
for general multiple-spin asymmetries are reviewed, taking as an example
the case `p+p
`L + L in which one, two or three spins are
analyzed. Some aspects related to quantum information and entangled
states are discussed. Some positivity domains for pairs and triplets
of spin parameters are displayed, together with the experimental points.
The case of inclusive reaction is also treated, taking as an example
the spin- and transverse momentum-dependent quark distributions.
PDF (230 Kb)
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