SSA in the target fragmentation region of SIDIS Aram Kotzinian Torino University & INFN On leave in absence from YerPhI, Armenia and JINR, Russia M.Anselmino, M.Boglione, U.D’Alesio, A.K., F.Murgia and A.Prokudin: PRD 71, 074006 (2005) A.K.: arXiv:hep-ph/0504081 Cahn and Sivers effects Phenomenology & Data in the CFR Intrinsic transverse momentum of partons in LEPTO Results for TFR of SIDIS Discussion & Conclusions SIR05, JLab, May 20, 2005 Aram Kotzinian

Unpolarized SIDIS & Cahn effect Ji et al: QCD factorization holds for approximation Quadratic in Linear in and proportional to SIR05, JLab, May 20, 2005 Aram Kotzinian

Comparison with data Non Gaussian tail; x, z and flavor dependence of intrinsic and fragmentation transv. momentum SIR05, JLab, May 20, 2005 Aram Kotzinian

Interpretation of Sivers effect Brodsky, Hwang & Schmidt, 2002: FSI + 2 Collins, 2002; Belitski, Ji &Yuan, 2003: Wilson gauge link Boer, Mulders & Teryaev, 1997: twist three gluonic pole In standard approach the effective treatment of the Sivers effect is adopted as correlation in quark distribution in transversely polarized nucleon SIR05, JLab, May 20, 2005 Aram Kotzinian

Parameterization for Sivers effect SIR05, JLab, May 20, 2005 Aram Kotzinian

Data SIR05, JLab, May 20, 2005 Aram Kotzinian

New HERMES data SIR05, JLab, May 20, 2005 Aram Kotzinian

CFR: TMD dependent description q h Well clasified correlations in distribution and fragmentation functions Sivers effect Boer-Mulders distribution Helicity distribution Collins effect in quark fragmentation SIR05, JLab, May 20, 2005 Aram Kotzinian

TFR & Fracture Functions q h 1994: Trentadue & Veneziano; Graudenz; … Fracture functions: probability of finding a parton q with momentum fraction x and a hadron h with the CMS energy fraction Eh/EN More correlations for TMD dependent FracFuncs SIR05, JLab, May 20, 2005 Aram Kotzinian

Azimuths in SIDIS In one-photon approximation the general structure of azimuthal angles dependences in polarized SIDIS can be found from very general principles (A.K. 1995). Valid both for CFR and TFR. SIR05, JLab, May 20, 2005 Aram Kotzinian

Hadronization Soft Strong Interaction SIR05, JLab, May 20, 2005 Aram Kotzinian

Quark intrinsic transverse momentum in LEPTO - Generate virtual photon – quark scattering in collinear configuration: - Before - After hard scattering - Generate intrinsic transverse momentum of quark (Gaussian kT) - Rotate in l-l’ plane - Generate uniform azimuthal distribution of quark (flat by default) - Rotate around virtual photon SIR05, JLab, May 20, 2005 Aram Kotzinian

Implementing Cahn and Sivers effects in LEPTO The common feature of Cahn and Sivers effects Unpolarized initial and final quarks Fragmenting quark-target remnant system is similar to that in default LEPTO but the direction of is now modulated Cahn: Sivers: Generate the final quark azimuth according to above distributions SIR05, JLab, May 20, 2005 Aram Kotzinian

Results: Cahn Imbalance of measured in TFR and CFR: neutrals? SIR05, JLab, May 20, 2005 Aram Kotzinian

Results: Sivers Predictions for JLab 12 GeV xF-dependence Red triangles with error bars – projected statistical accuracy for 1000h data taking (H.Avagyan). z and xBj-dependences SIR05, JLab, May 20, 2005 Aram Kotzinian

Results: Sivers JLab 12 GeV SIR05, JLab, May 20, 2005 Aram Kotzinian

SSA in PP-interactions E704. Curves: by Anselmino et al, STAR (hep-ex/0505024) xF<0 in PP corresponds to xF>0 in SIDIS. In both cases backward with respect to polarized proton flight direction in CMS. Both the active quark and the proton remnant are flying in forward direction. Which particles provide transverse momentum balance? SIR05, JLab, May 20, 2005 Aram Kotzinian

Discussion & Conclusions Both Cahn and Sivers effects are implemented in LEPTO. Possible effects of polarized hadronization were neglected. Existing data in CFR are well described by modified LEPTO The measured Cahn effect in the TFR is not well described Is there an universal mechanism describing SSA in SIDIS and PP interactions? It will be interesting to implement Cahn and Sivers effects in PHYTIA It is important to perform new measurements of both effects in the TFR (JLab, HERMES, Electron Ion Colliders) This will help better understand hadronization mechanism Do the neutral hadrons compensate Cahn effect in CFR? Is there a similarity with PP-reaction? Multihadron final states distributions can enhance effects Fracture Function “Global” analysis Classification of spin and TMD dependent correlations in Fracture Functions SIR05, JLab, May 20, 2005 Aram Kotzinian