1. 1 JLab, May 27, 2005 Aram Kotzinian Polarized Semi-Inclusive DIS in Current and Target Fragmentation Introduction The flavor separation of the quark helicity distributions The spin and azimuthal asymmetries in the current and target fragmentation regions Polarization of Λs produced in SIDIS of polarized leptons on unpolarized target Conclusions Aram Kotzinian Torino University & INFN On leave in absence from YerPhI, Armenia and JINR, Russia

2. 2 JLab, May 27, 2005 Aram Kotzinian Lepton-Nucleon EM Interactions Study of Confinement in QCD Structure of nucleon & hadronization dynamics Elastic – Form-factors Exclusive – GPDs DIS – DFs SIDIS: CFR: DFs & Fragmentation Functions TFR: Fracture Functions More general: Hadronization Functions Spin phenomena play crucial role in all channels

3. 3 JLab, May 27, 2005 Aram Kotzinian DIS

4. 4 JLab, May 27, 2005 Aram Kotzinian Nucleon Spin from polarized DIS Gluon Spin Nucleon spin Quark Spin Orbital Angular Momentum Spin Sum Rule COMPASS 2005 LSS 2005

5. 5 JLab, May 27, 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

6. 6 JLab, May 27, 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

7. 7 JLab, May 27, 2005 Aram Kotzinian Ed. Berger criterion (separation of CFR &TFR) The typical hadronic correlation length in rapidity is Illustrations from P. Mulders:

8. 8 JLab, May 27, 2005 Aram Kotzinian LUND String Fragmentation Soft Strong Interaction qq q Rank from diquark Rank from quark h Parton DF, hard X-section & Hadronization are factorized Implemented in LEPTO + JETSET (hadronization)

9. 9 JLab, May 27, 2005 Aram Kotzinian Flavor separation using SIDIS Leader & Stamenov, 2003: Non-negative strange quark polarization is almost impossible HERMES analysis

10. 10 JLab, May 27, 2005 Aram Kotzinian Purity method for flavor separation Purities are calculated using LEPTO N q q h

11. 11 JLab, May 27, 2005 Aram Kotzinian LO SIDIS in LEPTO - Before - After -Example: valence struck quark quarkTarget remnant Natural question: does Lund hadronization exactly correspond to independent quark fragmentation in the CFR with z>0.2? (A.K.2004) The important property of FFs is universality: 1.Independence of Bjorken variable x 2.Target type independence 3.Process type independence

12. 12 JLab, May 27, 2005 Aram Kotzinian Bjorken variable dependence of “FFs” in LEPTO The dependence of “FFs” on x cannot be attributed to Q 2 evolution

13. 13 JLab, May 27, 2005 Aram Kotzinian Target type dependence of “FFs” in LEPTO Example of target remnant: removed valence u-quark: There is dependence of “FFs” on the target type at 10% level

14. 14 JLab, May 27, 2005 Aram Kotzinian The primary hadrons produced in string fragmentation come from the string as a whole, rather than from an individual parton. LUND string fragmentation

15. 15 JLab, May 27, 2005 Aram Kotzinian Even for meson production in the CFR the hadronization in LEPTO is more complicated than SIDIS description with independent FFs Hadronization Functions (HF) More general framework -- Fracture Functions (Teryaev, T-odd, SSA…) We are dealing with LUND Hadronization Functions: LEPTO is a model for Fracture Functions: The dependence on target flavor is due to dependence on target remnant flavor quantum numbers. What about spin quantum numbers? Violation of naïve x-z factorization and isotopic invariance of FF

16. 16 JLab, May 27, 2005 Aram Kotzinian Dependence on target remnant spin state (unpolarized LEPTO) Example: valence u-quark is removed from proton. Default LEPTO: the remnant (ud) diquark is in 75% (25%) of cases scalar (vector) Even in unpolarized LEPTO there is a dependence on target remnant spin state (ud) 0 : first rank Λ is possible (ud) 1 : first rank Λ is impossible

17. 17 JLab, May 27, 2005 Aram Kotzinian Target remnant in Polarized SIDIS JETSET is based on SU(6) quark-diquark model Probabilities of different string spin configurations depend on quark and target polarizations, target type and process type 90% scalar 100% vector

18. 18 JLab, May 27, 2005 Aram Kotzinian Polarized SIDIS & HF -- spin dependent cross section and HFs These Eqs. coincide with those proposed by Gluk&Reya (polarized FFs). In contrast with FFs, HFs in addition to z depend on x and target type and double spin effect, as in DFs.

19. 19 JLab, May 27, 2005 Aram Kotzinian For validity of purity method most important is the second relation Asymmetry The standard expression for SIDIS asymmetry is obtained when

20. 20 JLab, May 27, 2005 Aram Kotzinian Toy model (A.K.2003) In JETSET there is a pointer indicating whether produced hadron is coming from quark or diquark end of the string. Symmetric LUND fragmentation: each string breaking starting with equal probabilities from q or qq end.

21. 21 JLab, May 27, 2005 Aram Kotzinian PEPSI MC Model A: default PEPSI Model B: neglect contribution of events to asymmetries with hadrons originated from diquark

22. 22 JLab, May 27, 2005 Aram Kotzinian Beam Energy Dependence Situation is different for higher energies: dependencies of “FFs” extracted from MC on x, target type and target remnant quantum numbers are weaker

23. 23 JLab, May 27, 2005 Aram Kotzinian LUND MC is proved to be capable to describe data in a wide range of kinematics. The new concept of (polarized) hadronization is introduced and studied using LEPTO event generator The hadronization in LEPTO is more general than simple LO x-z factorized picture with independent fragmentation, for example, it describes well TFR. It necessary to modify PEPSI MC event generator by including polarization in hadronization. The purity method have to be modified to include polarized HFs. Within this new approach one can include all hadrons (CFR+TFR) for flavor separation analysis. More studies on the accuracy of different methods of the polarized quark DF extraction using SIDIS asymmetries are needed. Alternative measurements are highly desirable SIDIS at different beam energies: COMPASS, JLab, EIC W production in polarized p+p collisions (Anti)neutrino DIS on polarized targets (Neutrino Factory) Conclusions 1

24. 24 JLab, May 27, 2005 Aram Kotzinian Melnitchouk & Thomas: Meson Cloud Model 100 % anticorrelated with target polarization contradiction with neutrino data for unpolarized target Longitudinal polarization of Λ in the TFR Λ-polarization in TFR

25. 25 JLab, May 27, 2005 Aram Kotzinian Karliner, Kharzeev, Sapozhnikov, Alberg, Ellis & A.K. Nucleon wave function contains an admixture with component: π,K masses are small at the typical hadronic mass scale: a strong attraction in the − channel. pairs from vacuum in state Intrinsic Strangeness Model Polarized proton: Spin crisis:

26. 26 JLab, May 27, 2005 Aram Kotzinian J.Ellis, A.K. & D.Naumov (2002)

27. 27 JLab, May 27, 2005 Aram Kotzinian qqq  Rank from diquark Rank from quark NOMAD (43.8 GeV)COMPASS (160 GeV) No clean separation of the quark and diquark fragmentation Λ parent

28. 28 JLab, May 27, 2005 Aram Kotzinian Λ polarization in quark & diquark fragmentation Λ polarization from the diquark fragmentation Λ polarization from the quark fragmentation

29. 29 JLab, May 27, 2005 Aram Kotzinian Spin Transfer We use Lund string fragmentation model incorporated in LEPTO6.5.1 and JETSET7.4. We consider two extreme cases when polarization transfer is nonzero: model A: the hyperon contains the stuck quark: Rq = 1 the hyperon contains the remnant diquark: Rqq = 1 model B: the hyperon originates from the stuck quark: Rq ≥ 1 the hyperon originates from the remnant diquark: Rqq ≥ 1

30. 30 JLab, May 27, 2005 Aram Kotzinian Fixing free parameters We vary two correlation coefficients ( and ) in order to fit our models A and B to the NOMAD Λ polarization data. We fit to the following 4 NOMAD points to find our free parameters:

31. 31 JLab, May 27, 2005 Aram Kotzinian Results Predictions for JLab 5.75 GeV

32. 32 JLab, May 27, 2005 Aram Kotzinian Predictions for CLAS Predictions for x F -dependence at JLab 12 GeV Red squares with error bars – projected statistical accuracy for 1000h data taking (H.Avagyan).

33. 33 JLab, May 27, 2005 Aram Kotzinian Predictions for EIC 5 GeV/c electron + 50 GeV/c proton, Good separation of the quark and diquark fragmentation allows to distinguish between different spin transfer mechanisms from quark and diquark

34. 34 JLab, May 27, 2005 Aram Kotzinian Conclusions 2 Predictions for Λ polarization are very sensitive to production mechanism A phenomenological polarized intrinsic strangeness + SU(6) model is able to describe all available data on longitudinal polarization of Λ in full kinematic range New measurements at different energies will serve as a test for proposed models

35. 35 JLab, May 27, 2005 Aram Kotzinian Unpolarized SIDIS & Cahn effect x & z are light cone variables defined with respect z & axes No exact factorization ! M.Anselmino, M.Boglione, U.D’Alesio, A.K., F.Murgia and A.Prokudin: PRD 71, 074006 (2005) A.K.: arXiv:hep-ph/0504081

36. 36 JLab, May 27, 2005 Aram Kotzinian Unpolarized SIDIS & Cahn effect Ji et al: QCD factorization holds for Quadratic in Linear in and proportional to approximation

37. 37 JLab, May 27, 2005 Aram Kotzinian Comparison with data Non Gaussian tail; x, z and flavor dependence of intrinsic and fragmentation transv. momentum

38. 38 JLab, May 27, 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

39. 39 JLab, May 27, 2005 Aram Kotzinian Parameterization for Sivers effect

40. 40 JLab, May 27, 2005 Aram Kotzinian Data

41. 41 JLab, May 27, 2005 Aram Kotzinian New HERMES data

42. 42 JLab, May 27, 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

43. 43 JLab, May 27, 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

44. 44 JLab, May 27, 2005 Aram Kotzinian Results: Cahn Imbalance of measured in TFR and CFR: neutrals?

45. 45 JLab, May 27, 2005 Aram Kotzinian Results: Sivers Predictions for x F -dependence at JLab 12 GeV Red triangles with error bars – projected statistical accuracy for 1000h data taking (H.Avagyan). z and x Bj -dependences

46. 46 JLab, May 27, 2005 Aram Kotzinian Results: Sivers JLab 12 GeV

47. 47 JLab, May 27, 2005 Aram Kotzinian SSA in PP-interactions E704. Curves: by Anselmino et al, STAR (hep-ex/0505024) Both the active quark and the polarized proton remnant are flying in forward direction. Which final hadrons provide transverse momentum balance? h P P STST

48. 48 JLab, May 27, 2005 Aram Kotzinian Conclusions 3 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 “Global” analysis Classification of spin and TMD dependent correlations in Fracture Functions

49. 49 JLab, May 27, 2005 Aram Kotzinian Conclusions Spin phenomena in SIDIS can play very important role for modeling and understanding the QCD dynamics Access to TFR opens a new field both for theoretical and experimental investigations JLab@12 GeV is ideally placed to make important breakthroughs over a wide spectrum of discovery in nucleon structure and hadronization dynamics Thanks for hospitality @ JLab

50. 50 JLab, May 27, 2005 Aram Kotzinian Support Slides

51. 51 JLab, May 27, 2005 Aram Kotzinian HERMES check