Longitudinal target polarization dependence of polarization and polarized

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

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

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

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

NOMAD data Madrid, April 27, 2009 Aram Kotzinian 5

Λ polarization J. Ellis, A. K. , D. Naumov and M. Sapozhnikov EPJ. C 52: 283 -294, 2007 μ′ μ′ Λ s u μ u -s μ Λ P P (ud)0 Rqq<Rq: spin transfer only Rq<Rqq: spin transfer only from intrinsic strangeness from final quark Madrid, April 27, 2009 Aram Kotzinian 6

Unpolarized target SU(6), CTEQ 5 L NOMAD tuning used LEPTO MC Best description with SU(6) s-bar purity model for spin transfer. polarization = s(x) filter Madrid, April 27, 2009 Aram Kotzinian 7

Quark type fraction in anti-Lambda production LEPTO MC s u d s with CTEQ 5 L and COMPASS cuts In contrast to K u d u production asymmetry, s s d here mainly s-bar contributes to s u d Madrid, April 27, 2009 d u s Aram Kotzinian 8

PDFs Madrid, April 27, 2009 Aram Kotzinian 9

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

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

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

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

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

Two inputs for Pq=Δq/q DSSV+MRST 02 GRSV+GRV 2008 2000 Madrid, April 27, 2009 Aram Kotzinian 15

COMPASS cuts Q 2 > 1 (Ge. V/c)2; 0. 2 < y <0. 9 Primary vertex: -100 < z < 100 or -30 < z < 30 (cm) Decay vertex: 35 < zdec < 140 (cm) Vertexes colinearity cut: θcol = 0. 01 Decay particles momentum: p > 1 Ge. V/c Feynman variable: 0. 05 < x. F < 0. 5 Λ rest frame decay angle cut: cos(θ*) < 0. 6 Madrid, April 27, 2009 Aram Kotzinian 16

Dependence on pol. PDFs To verify sign change of Δs measure in two bins of x: x < 0. 03 and 0. 03 <x Madrid, April 27, 2009 Aram Kotzinian 17

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

Conclusions (Anti)Lambda polarization measurements in SIDIS of polarized leptons off unpolarized and polarized targets can shed light unpolarized and polarized sbar 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 Madrid, April 27, 2009 Aram Kotzinian 19