1 SSH05, BNL, June 2, 2005 Aram Kotzinian SSA in the target fragmentation region of SIDIS Cahn and Sivers effects Phenomenology & Data in the CFR Intrinsic transverse momentum of partons in LEPTO Results for TFR Discussion & Conclusions 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, (2005) A.K.: arXiv:hep-ph/

2 SSH05, BNL, June 2, 2005 Aram Kotzinian Unpolarized SIDIS & Cahn effect x & z are light cone variables defined with respect z & axes No exact factorization !

3 SSH05, BNL, June 2, 2005 Aram Kotzinian approximation Ji et al: QCD factorization holds for Quadratic in Linear in and proportional to

4 SSH05, BNL, June 2, 2005 Aram Kotzinian Comparison with data: 1 EMC, 280 GeV muon SIDIS

5 SSH05, BNL, June 2, 2005 Aram Kotzinian Comparison with data: 2

6 SSH05, BNL, June 2, 2005 Aram Kotzinian Comparison with data: 3

7 SSH05, BNL, June 2, 2005 Aram Kotzinian Comparison with data: 4 Non Gaussian tail; x, z and flavor dependence of intrinsic and fragmentation transverse momentum ?

8 SSH05, BNL, June 2, 2005 Aram Kotzinian 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 Sivers effect

9 SSH05, BNL, June 2, 2005 Aram Kotzinian Parameterization for Sivers effect

10 SSH05, BNL, June 2, 2005 Aram Kotzinian Asymmetry

11 SSH05, BNL, June 2, 2005 Aram Kotzinian Data

12 SSH05, BNL, June 2, 2005 Aram Kotzinian New HERMES data

13 SSH05, BNL, June 2, 2005 Aram Kotzinian SIDIS in LO QCD: CFR Well classified correlations in TMD distr. and fragm. functions Sivers distribution Boer distribution Helicity distribution Collins effect in quark fragmentation N q q h p Mulders distribution

14 SSH05, BNL, June 2, 2005 Aram Kotzinian SIDIS in LO QCD: TFR N q h 1994: Trentadue & Veneziano; Graudenz; … Fracture functions: conditional probability of finding a parton q with momentum fraction x and a hadron h with the CMS energy fraction z More correlations for TMD dependent FracFuncs

15 SSH05, BNL, June 2, 2005 Aram Kotzinian Ed. Berger criterion: separation of quark and target remnant fragmentations) The typical hadronic correlation length in rapidity is Illustrations from P. Mulders: EIC: good separation of two mechanisms

16 SSH05, BNL, June 2, 2005 Aram Kotzinian LUND String Fragmentation Soft Strong Interaction qq q Rank from diquark Rank from quark h LEPTO: Parton DF, hard X-section & Hadronization are factorized Double spin effect – polarized hadronization

17 SSH05, BNL, June 2, 2005 Aram Kotzinian Asymmetry in longitudinally polarized SIDIS The standard expression for SIDIS asymmetry is obtained when at HERMES energies in LEPTO ~10-15% A.K.: arXiv:hep-ph/ ; EPJC (2005)

18 SSH05, BNL, June 2, 2005 Aram Kotzinian Quark intrinsic transverse momentum in LEPTO - Generate virtual photon – quark scattering in collinear configuration: - Before - After hard scattering - Rotate in l-l’ plane - Generate intrinsic transverse momentum of quark (Gaussian k T ) - Generate uniform azimuthal distribution of quark (flat by default) - Rotate around virtual photon

19 SSH05, BNL, June 2, 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

20 SSH05, BNL, June 2, 2005 Aram Kotzinian Results: Cahn Imbalance of measured in TFR and CFR: neutrals?

21 SSH05, BNL, June 2, 2005 Aram Kotzinian Results: Sivers Predictions for JLab 12 GeV x F -dependence Red triangles with error bars – projected statistical accuracy for 1000h data taking (H.Avagyan). z and x Bj -dependences

22 SSH05, BNL, June 2, 2005 Aram Kotzinian Results: Sivers JLab 12 GeV

23 SSH05, BNL, June 2, 2005 Aram Kotzinian SSA in PP-interactions E704. Curves: by Anselmino et al, STAR hep-ex/ More complicated string (color) configurations in the final state. Both the active quark and the polarized proton remnant are flying in forward direction. Which picture gives dominant contribution? h P P STST h P P STST Which final hadrons provide transverse momentum balance? Look at forward baryons

24 SSH05, BNL, June 2, 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? Multihadron final states distributions can enhance effects Is there a similarity with PP-reaction? Fracture Function Classification of spin and TMD dependent correlations in Fracture Functions “Global” analysis

25 SSH05, BNL, June 2, 2005 Aram Kotzinian Thanks to SSA05 organizers for BNL