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SSA in SIDIS: Cahn and Sivers effects, phenomenology, and data in the CFR

This paper discusses the Cahn and Sivers effects in Semi-Inclusive Deep Inelastic Scattering (SIDIS), including their phenomenology and data in the Current Fragmentation Region (CFR). It also explores the intrinsic transverse momentum of partons in LEPTO and presents results for the TFR of SIDIS.

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SSA in SIDIS: Cahn and Sivers effects, phenomenology, and data in the CFR

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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 of SIDIS • 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 Ji et al: QCD factorization holds for approximation Quadratic in Linear in and proportional to AramKotzinian

  3. Comparison with data Non Gaussian tail; x, z and flavor dependence of intrinsic and fragmentation transv. momentum AramKotzinian

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

  5. Parameterization for Sivers effect AramKotzinian

  6. Data AramKotzinian

  7. New HERMES data AramKotzinian

  8. CFR: TMD dependent description h q q N Well clasified correlations in distribution and fragmentation functions Sivers effect Boer-Mulders distribution Helicity distribution Collins effect in quark fragmentation AramKotzinian

  9. TFR & Fracture Functions q N 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 AramKotzinian

  10. 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. AramKotzinian

  11. Hadronization Soft Strong Interaction AramKotzinian

  12. 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

  13. 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

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

  15. 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

  16. Results: Sivers JLab 12 GeV AramKotzinian

  17. 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? AramKotzinian

  18. 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 Discussion & Conclusions AramKotzinian

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