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SSA in the target fragmentation region of SIDIS

SSA in the target fragmentation region of SIDIS. Aram Kotzinian Torino University & INFN On leave in absence from YerPhI, Armenia and JINR, Russia. Cahn and Sivers effects Phenomenology & Data in the CFR Intrinsic transverse momentum of partons in LEPTO Results for TFR

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SSA in the target fragmentation region of SIDIS

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

  2. Unpolarized SIDIS & Cahn effect x & z are light cone variables defined with respect z & axes No exact factorization ! AramKotzinian

  3. approximation Ji et al: QCD factorization holds for Quadratic in Linear in and proportional to AramKotzinian

  4. Comparison with data: 1 EMC, 280 GeV muon SIDIS AramKotzinian

  5. Comparison with data: 2 AramKotzinian

  6. Comparison with data: 3 AramKotzinian

  7. Comparison with data: 4 ? Non Gaussian tail; x, z and flavor dependence of intrinsic and fragmentation transverse momentum AramKotzinian

  8. 2 + In standard approach the effective treatment of the Sivers effect is adopted as correlation in quark distribution in transversely polarized nucleon Sivers effect Brodsky, Hwang & Schmidt, 2002: FSI Collins, 2002; Belitski, Ji &Yuan, 2003: Wilson gauge link Boer, Mulders & Teryaev, 1997: twist three gluonic pole AramKotzinian

  9. Parameterization for Sivers effect AramKotzinian

  10. Asymmetry AramKotzinian

  11. Data AramKotzinian

  12. New HERMES data AramKotzinian

  13. SIDIS in LO QCD: CFR h q q N p Well classified correlations in TMD distr. and fragm. functions Sivers distribution Mulders distribution Boer distribution Helicity distribution Collins effect in quark fragmentation AramKotzinian

  14. SIDIS in LO QCD: TFR q N 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 AramKotzinian

  15. 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 AramKotzinian

  16. LUND String Fragmentation q h Rank from diquark Rank from quark Soft Strong Interaction qq LEPTO: Parton DF, hard X-section & Hadronizationare factorized Double spin effect – polarized hadronization AramKotzinian

  17. Asymmetry in longitudinally polarized SIDIS A.K.: arXiv:hep-ph/0410093; EPJC (2005) The standard expression for SIDIS asymmetry is obtained when at HERMES energies in LEPTO ~10-15% AramKotzinian

  18. 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 AramKotzinian

  19. 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 AramKotzinian

  20. Results: Cahn Imbalance of measured in TFR and CFR: neutrals? AramKotzinian

  21. 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 AramKotzinian

  22. Results: Sivers JLab 12 GeV AramKotzinian

  23. SSA in PP-interactions h ST P P h ST P P E704. Curves: by Anselmino et al, STAR hep-ex/0505024 Which final hadrons provide transverse momentum balance? Look at forward baryons 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? AramKotzinian

  24. 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 Discussion & Conclusions AramKotzinian

  25. Thanks to SSA05 organizers for hospitality @ BNL AramKotzinian

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