Intrinsic transverse momentum and the Sivers effect Aram

Intrinsic transverse momentum and the Sivers effect # Aram Kotzinian Torino University & INFN On leave in absence from Yer. Ph. I, 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 1

SIDIS Transversity workshop Trento, June 16, 2004 Aram Kotzinian 2

Intrinsic transverse momentum role Gluon polarization measurement LP QCDCompton PGF R strongly depends on the intrinsic Transversity workshop Trento, June 16, 2004 Aram Kotzinian and fragmentation 3

Unpolarized SIDIS & Cahn effect Transversity workshop Trento, June 16, 2004 Aram Kotzinian 4

approximation Ji et al: QCD factorization holds for Transversity workshop Trento, June 16, 2004 Aram Kotzinian 5

Comparison with data EMC, 280 Ge. V muon SIDIS Transversity workshop Trento, June 16, 2004 Aram Kotzinian 6

Hadron transverse momentum dependence Transversity workshop Trento, June 16, 2004 Aram Kotzinian 7

Collins Effect azimuthal modulation of transversely polarized quark FF Front view Side 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 8

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 9

SSA Analyzing power: Analysis by Anselmino et al, E 704 STAR Only Sivers effect Transversity workshop Trento, June 16, 2004 Only Collins effect Aram Kotzinian 10

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 11

Parameterization for Sivers effect Transversity workshop Trento, June 16, 2004 Aram Kotzinian 12

Anselmino et al for E 704 SSA u-quark d-quark Our parameterization: opposite sign & high values at small x Transversity workshop Trento, June 16, 2004 Aram Kotzinian 13

Results: p on P & D targets Transversity workshop Trento, June 16, 2004 Aram Kotzinian 14

Results: K on D target Transversity workshop Trento, June 16, 2004 Aram Kotzinian 15

Transversity workshop Trento, June 16, 2004 Aram Kotzinian 16

Transversity workshop Trento, June 16, 2004 Aram Kotzinian 17

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 18

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 19

Electron Ion Collider Transversity workshop Trento, June 16, 2004 Aram Kotzinian 20

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 21

End of Story? Zoology of Frac. Fun Transversity workshop Trento, June 16, 2004 Aram Kotzinian 22

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 23