Intrinsic transverse momentum and the Sivers effect # Aram Kotzinian Torino University & INFN On leave in absence from YerPhI, Armenia and JINR, Russia Intrinsic transverse momentum of quarks Why it is actual Cahn effect Single target spin asymmetries Sivers effect Collins effect In collaboration with M. Anselmino, M. Boglione, U. D'Alesio, F. Murgia & A. Prokudin Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop SIDIS Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Intrinsic transverse momentum role Gluon polarization measurement LP QCDCompton PGF R strongly depends on the intrinsic and fragmentation Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Unpolarized SIDIS & Cahn effect Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop approximation Ji et al: QCD factorization holds for Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Comparison with data EMC, 280 GeV muon SIDIS Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Hadron transverse momentum dependence Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Collins Effect azimuthal modulation of transversely polarized quark FF Side view Front view Up-Down asymmetry = 0 Nonzero Left-Right asymmetry Schaefer-Teryaev SR: hadrons transverse momenta are compensated in the quark fragmentation Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Sivers Effect Azimuthal modulation of quark transverse momentum for a transversely polarized nucleon Unpolarized DF: Polarized DF: Quark transverse momentum is compensated by that of target remnant Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop SSA Analyzing power: Only Sivers effect Only Collins effect Analysis by Anselmino et al, E704 STAR Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop HERMES SSA One can describe the data using only Collins effect Schweitzer & Bacchetta: there is a room for Sivers effect Efremov, Goeke & Schweitzer: one can neglect the Sivers effect Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Parameterization for Sivers effect Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Anselmino et al for E704 SSA u-quark d-quark Our parameterization: opposite sign & high values at small x Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Results: p on P & D targets Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Results: K on D target Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Quark intrinsic transverse momentum in LEPTO - Generate virtual photon – quark scattering in collinear configuration: - Before - After - Generate intrinsic transverse momentum of quark (Gaussian) - Rotate - Generate uniform azimuthal distribution of quark - Rotate - Generate quark azimuthal angle according to Sivers distribution Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Modified LEPTO MC predictions for JLAB SSA Opposite signs of asymmetry in the target and current fragmentation In principle, one can check origin of by measuring it in the TFR Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Electron Ion Collider Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Modified LEPTO MC predictions for EIC SSA Opposite signs of asymmetry in the target and current fragmentation In principle, one can check origin of by measuring it in the TFR Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop End of Story? Zoology of FracFun Transversity workshop Trento, June 16, 2004 Aram Kotzinian

Transversity workshop Conclusions Intrinsic transverse momentum in simple parton model approach allows to describe Hadron transverse momentum dependence in SIDIS Cahn effect HERMES SSA data on longitudinally polarized target It is important to investigate the SSA in the TFR Sivers effect? Collins effect from target remnant hadronization? We need more precise data on transversely polarized targets Transversity workshop Trento, June 16, 2004 Aram Kotzinian