1. 1 Madrid, April 27, 2009 Aram Kotzinian Longitudinal target polarization dependence of Λ polarization and polarized strangeness PDF Λ polarization Unpolarized target Strangeness distribution in nucleon Polarized target Polarized strangeness in polarized nucleon Conclusions Aram Kotzinian CEA-Saclay, IRFU/Service de Physique Nucléaire, 91191 Gif-sur-Yvette, France On leave in absence from YerPhI, Armenia and JINR, Russia DIS 2009, 26-30 April 2009, Madrid

2. 2 Madrid, April 27, 2009 Aram Kotzinian Simple model: LO, independent fragmentation for current fragmentation region Fraction of events with hard scattering off s-bar (s-bar purity)

3. 3 Madrid, April 27, 2009 Aram Kotzinian Intrinsic Strangeness Model (ISM) for Λ polarization P u (ud) 0 s s - Λ μ μ′μ′ R qq <R q : spin transfer from intrinsic strangeness and polarized diquark via heavier hyperons P u (ud) 0 Λ μ μ′μ′ R q <R qq : spin transfer only from final quark J.Ellis,M.Karliner,D.Kharzeev,M.G.Sapozhnikov, 1995 J.Ellis, D.Kharzeev, A.K., 1996 J. Ellis, A. K. & D. Naumov, 2002 TFR CFR

4. 4 Madrid, April 27, 2009 Aram Kotzinian Spin transfer in SIDIS Spin transfer from qq side Spin transfer from q side

5. 5 Madrid, April 27, 2009 Aram Kotzinian NOMAD data

6. 6 Madrid, April 27, 2009 Aram Kotzinian Λ polarization P u s s - μ μ′μ′ R qq <R q : spin transfer only from intrinsic strangeness Λ P u (ud) 0 Λ μ μ′μ′ R q <R qq : spin transfer only from final quark J.Ellis, A.K., D.Naumov and M.Sapozhnikov EPJ.C52:283-294,2007

7. 7 Madrid, April 27, 2009 Aram Kotzinian NOMAD tuning used Best description with SU(6) model for spin transfer. polarization = s(x) filter Unpolarized target LEPTO MC s-bar purity SU(6), CTEQ5L

8. 8 Madrid, April 27, 2009 Aram Kotzinian Quark type fraction in anti-Lambda production LEPTO MC with CTEQ5L and COMPASS cuts In contrast to K production asymmetry, here mainly s-bar contributes to u d s s s s s s u u u u u d d d d d

9. 9 Madrid, April 27, 2009 Aram Kotzinian PDFs

10. 10 Madrid, April 27, 2009 Aram Kotzinian Hyperon production x-section and polarization for polarized beam and target Target polarization sign is written explicitly Beam polarization contains sign From general considerations for double and triple longitudinal polarization observables: Triple-spin effect

11. 11 Madrid, April 27, 2009 Aram Kotzinian Polarization Asymmetry Polarization asymmetry

12. 12 Madrid, April 27, 2009 Aram Kotzinian Factorized LO QCD parton model We can neglect pol.dep. part in denom. ISM expression is more complicated, but results are almost unchanged

13. 13 Madrid, April 27, 2009 Aram Kotzinian in LO QCD parton SU(6) model

14. 14 Madrid, April 27, 2009 Aram Kotzinian ISM calculations using LEPTO Separately calculate numerator and denominator by reweighting each generated event Nomad settings and Symbolic notations: Lund Model is realization of Fracture Functions. Spin transfer via heavy hyperons is taken into account.

15. 15 Madrid, April 27, 2009 Aram Kotzinian Two inputs for P q =Δq/q DSSV+MRST02 2008 GRSV+GRV 2000

16. 16 Madrid, April 27, 2009 Aram Kotzinian COMPASS cuts Q 2 > 1 (GeV/c) 2 ; 0.2 < y <0.9 Primary vertex: -100 < z < 100 or -30 < z < 30 (cm) Decay vertex: 35 < z dec < 140 (cm) Vertexes colinearity cut: θ col = 0.01 Decay particles momentum: p > 1 GeV/c Feynman variable: 0.05 < x F < 0.5 Λ rest frame decay angle cut: cos(θ * ) < 0.6

17. 17 Madrid, April 27, 2009 Aram Kotzinian Dependence on pol. PDFs To verify sign change of Δs measure in two bins of x: x < 0.03 and 0.03 <x

18. 18 Madrid, April 27, 2009 Aram Kotzinian COMPASS preliminary Sing change of ΔP corresponds to DSSV PDFs

19. 19 Madrid, April 27, 2009 Aram Kotzinian Conclusions (Anti)Lambda polarization measurements in SIDIS of polarized leptons off unpolarized and polarized targets can shed light unpolarized and polarized s- bar distributions in nucleon (Anti)Lambda polarization on unpolarized target strongly depends on strangeness PDF Polarization asymmetry strongly depends on strangeness polarization shape (Anti)Lambda polarization in SIDIS is well suited filter for nucleon strangeness study