1. 1EIC-2004, March 17Aram Kotzinian Hyperon Physics and Target Fragmentation L polarization Transverse Longitudinal Single target spin asymmetries Collins effect Sivers effect Aram Kotzinian Torino University & INFN On leave in absence from YerPhI, Armenia and JINR, Russia

2. 2EIC-2004, March 17Aram Kotzinian SIDIS

3. 3EIC-2004, March 17Aram Kotzinian Large branching ratio in the charged hadron channel: Unique tool for polarization study due to self-analyzing parity violating weak decay Simple spin structure in the naïve quark model: (ud)-diquark is a spin and isospin singlet (s)-quark carries whole spin of L Why L? P In the L rest frame

4. 4EIC-2004, March 17Aram Kotzinian Transverse Polarization of L in pp/A reactions z Normal to production plane Empiric relation: L n x P

5. 5EIC-2004, March 17Aram Kotzinian Models for Transverse Polarization DeGrand & Miettinen model (1981) Quark recombination Anderson, Gustafson & Ingelman (1979) String fragmentation Barni, Preparata & Ratcliffe (1992) Diffractive triple-Regge model Anselmino, Boer, D’Alesio & Murgia (2001) New polarizing Fragmentation Functions

6. 6EIC-2004, March 17Aram Kotzinian De Grand & Miettinen model An empirical rule for spin direction of recombining quark: Slow partons – Down (L), fast partons – Up SU(6) wave functions for baryons Semiclassical dynamic is based on Thomas precession New term in effective interaction Hamiltonian, where Thomas frequency is fast partons – Up

7. 7EIC-2004, March 17Aram Kotzinian Anderson, Gustafson & Ingelman model Semiclassical string fragmentation model Vacuum quantum numbers of quark-antiquark pair: -state Normal to production plane – out of picture -pair orbital moment is compensated by spin Negative transverse polarization of L

8. 8EIC-2004, March 17Aram Kotzinian Interference between diagrams with different intermediate baryons give rise to polarization Barni, Preparata & Ratcliffe

9. 9EIC-2004, March 17Aram Kotzinian Polarizing Fragmentation Functions In unpolarized quark fragmentation with nonzero transverse momentum,, L can be transversely polarized L n Probabilistic interpretation – no interference effects

10. 10EIC-2004, March 17Aram Kotzinian Some Open Questions No transverse polarization observed at LEP Positive transverse polarization at HERMES Qualitatively can be explained in DM model with VMD approach Parton model: u-quark dominance? Compare with neutrino data.

11. 11EIC-2004, March 17Aram Kotzinian TFR of SIDIS Trentadue & Veneziano: fracture function – probability of finding a parton q with momentum fraction x and a hadron h with the CMS energy fraction in the proton.

12. 12EIC-2004, March 17Aram Kotzinian Melnitchouk & Thomas: 100 % anticorrelated with target polarization contradiction with neutrino data for unpolarized target Longitudinal polarization of L in the TFR in neutrino SIDIS Meson Cloud Model

13. 13EIC-2004, March 17Aram 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:

14. 14EIC-2004, March 17Aram Kotzinian Ed. Berger criterion The typical hadronic correlation length in rapidity is Illustrations from P. Mulders: HERMES: 4 GeV; COMPASS: 11 GeV; EIC(5+50, y>0.4): 24GeV

15. 15EIC-2004, March 17Aram Kotzinian L production in 500 GeV/c π−-Nucleon Production Fermilab E791 Collaboration, hep-ph/0009016 Significant target influence in the projectile fragmentation region

16. 16EIC-2004, March 17Aram Kotzinian qqq  Rank from diquark Rank from quark Tagging scheme for a hyperon which contains: Struck quarkRemnant diquark R q =1 (A) R q  1 & Rqq  1 (B) R qq =1 (A) R qq  1 & Rq  1 (B) NOMAD (43.8 GeV)COMPASS (160 GeV) No clean separation of the quark and diquark fragmentation

17. 17EIC-2004, March 17Aram Kotzinian J.Ellis, A.K. & D.Naumov (2002)

18. 18EIC-2004, March 17Aram Kotzinian Λ polarization in quark & diquark fragmentation Λ polarization from the diquark fragmentation Λ polarization from the quark fragmentation I – nonrelativistic SU(6) wave functions II – flavor SU(3) & polarized DIS data for baryon octet:

19. 19EIC-2004, March 17Aram 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

20. 20EIC-2004, March 17Aram 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:

21. 21EIC-2004, March 17Aram Kotzinian Results

22. 22EIC-2004, March 17Aram Kotzinian Predictions for COMPASS

23. 23EIC-2004, March 17Aram 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 in the quark fragmentation

24. 24EIC-2004, March 17Aram Kotzinian Collins Effect Front view Side view azimuthal modulation of transversely polarized quark FF Up-Down asymmetry = 0 Nonzero Left-Right asymmetry Schaefer-Teryaev SR: hadrons transverse momenta are compensated in the quark fragmentation

25. 25EIC-2004, March 17Aram Kotzinian Sivers Effect Azimuthal modulation of quark transverse momentum for a transversely polarized nucleon Unpolarized DF: Polarized DF: Quark transverse momentum is compensated by that of diquark One can incorporate into LEPTO MC SIDIS event generator

26. 26EIC-2004, March 17Aram Kotzinian SSA Analyzing power: Only Sivers effect Only Collins effect Analysis by Anselmino et al, E704 STAR

27. 27EIC-2004, March 17Aram Kotzinian Open points – HERMES data Filled points – MC, only Sivers Only Collins HERMES SSA

28. 28EIC-2004, March 17Aram Kotzinian Anselmino et al for E704 SSA Test parameterization: opposite sign & high values at small x Parameterization for

29. 29EIC-2004, March 17Aram Kotzinian Modified LEPTO MC predictions for EIC SSA Opposite signs of asymmetry in the target and current fragmentation E704 SSA – diquark fragmentation ?

30. 30EIC-2004, March 17Aram Kotzinian Modified LEPTO MC predictions for EIC SSA Opposite signs of asymmetry in the target and current fragmentation In principle, one can check origin of by measuring it in the TFR

31. 31EIC-2004, March 17Aram Kotzinian Conclusions We have no well developed QCD framework to describe hadron (hyperon) production and polarization in the TFR EIC will allow To distinguish between different models of L polarization (both longitudinal and transverse) To check the target independence of spontaneous L transverse polarization in the TFR (proton scattering on virtual photon) To investigate the azimuthal SSA in the TFR Sivers effect Collins effect from target remnant (diquark) hadronization?