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Spin observables and spin structure functions: inequalities and dynamics
Artru X., Elchikh M., Richard J.-M., Soffer J., Teryaev O.V.
Physics Reports 470 (2009) 1-92 - http://hal.in2p3.fr/in2p3-00238395
Physique/Physique des Hautes Energies - Phénoménologie
Spin observables and spin structure functions: inequalities and dynamics
X. Artru1, M. Elchikh, J.-M. Richard2, J. Soffer, O.V. Teryaev
1 :  IPNL - Institut de Physique Nucléaire de Lyon
CNRS : UMR5822 – IN2P3 – Université Claude Bernard - Lyon I (UCBL)
2 :  LPSC - Laboratoire de Physique Subatomique et de Cosmologie
CNRS : UMR5821 – IN2P3 – Université Joseph Fourier - Grenoble I – Institut Polytechnique de Grenoble - Grenoble Institute of Technology
53 avenue des Martyrs - 38026 Grenoble Cedex
Model-independent identities and inequalities relating the various spin observables of a reaction are reviewed in a unified formalism, together with their implications for dynamical models, their physical interpretation, and the quantum aspects of the information carried by spins, in particular entanglement. These constraints between observables can be obtained from the explicit expression of the observables in terms of a set of amplitudes, a non-trivial algebraic exercise which can be preceded by numerical simulation with randomly chosen amplitudes, from anticommutation relations, or from the requirement that any polarisation vector is less than unity. The most powerful tool is the positivity of the density matrices describing the reaction or its crossed channels, with a projection to single out correlations between two or three observables. For the exclusive reactions, the cases of the strangeness-exchange proton-antiproton scattering and the photoproduction of pseudoscalar mesons are treated in some detail: all triples of observables are constrained, and new results are presented for the allowed domains. The positivity constraints for total cross-sections and single-particle inclusive reactions are reviewed, with application to spin-dependent structure functions and parton distributions. The corresponding inequalities are shown to be preserved by the evolution equations of QCD.

Articles dans des revues avec comité de lecture
Physics Reports (Phys. Rep.)
Publisher Elsevier
ISSN 0370-1573 

125 pages, 37 figures, pdflatex, accepted by Physics Reports
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