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STAR Asia Meeting

Hyperon Polarization Physics at RHIC. STAR Asia Meeting. Liang Zuo-tang ( 梁作堂 ). School of Physics, Shandong University 山东大学物理学院. Pusan, May 8, 2009. Introduction Spin transfer in fragmentation and hyperon polarization in pp collisions

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STAR Asia Meeting

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  1. Hyperon Polarization Physics at RHIC STAR Asia Meeting Liang Zuo-tang (梁作堂) School of Physics, Shandong University 山东大学物理学院 Pusan, May 8, 2009 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  2. Introduction Spin transfer in fragmentation and hyperon polarization in pp collisions Spin structure of nucleon sea and anti-hyperon polarization in pp collisions Hyperon polarization in AA collisions Summary Contents 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  3. B H parity violating term in the rest frame of H Hyperon polarization can easily be measured. an important role in high energy spin physics. Introduction: Hyperon polarization polarization of H Spin self analyzing parity violating weak decay HB+M : 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  4. Spin transfer: Hyperon polarization in polarized pp collisions longitudinally, transversely polarized fragmentation function spin structure of nucleon Induced: Hyperon polarization in unpolarized hh collisions transversely w.r.t. the production plane higher twist effects (parton correlations) Global polarization in AA collisions transversely w.r.t. the reaction plane spin-orbit interaction in QCD Introduction: Hyperon polarization at RHIC Two classes of hyperon polarization phenomena: study of all the three aspects of high energy spin physics in strong interaction 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  5. jet 1 jet 2 Spin transfer in : factorization Spin-dependent parton distributions: Polarized fragmentation function: Spin transfer in the elementary process: 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  6. Spin transfer in the elementary processes e.g., Xu, Liu & Liang, PRD (2002) Calculable using pQCD in longitudinally polarized case (in helicity frame) 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  7. Cannot be calculated using pQCD No enough data available to parameterize Model Polarized fragmentation function: general description and divide the fragmentation function into: We consider (unpolarized) (polarized) the decay contribution part can be calculated: Need a model for 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  8. Calculating according to the origin of H Polarized fragmentation function: model Further divide: first rank contribution, i.e. H contains the initial quark qf Model: spin transfer only to the first rank hadron. polarization spin transfer constant: contribution of spin of qf to the spin of H, calculated from SU(6) wave-function or DIS data number of qf in H z-dependence is given. the only unknown is a constant. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  9. Spin transfer Polarized fragmentation function: model The unpolarized quantities are obtained from PYTHIA Boros & Liang, PRD (1998) Zhou, Chen, Liang and Xu, PRD(2009). 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  10. Lambda polarization in e+e- annihilation at the Z-pole fragmentation Polarized fragmentation function: test E.g., at the Z0 pole, <Pf(q)>=-0.94 for qf=s,d,b; <Pf(q)>=-0.67 for qf=u,c. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  11. Lambda polarization in e+e- annihilation at the Z-pole Polarized fragmentation function: test SU(6) • z-dependence is well reproduced. • SU(6) even better. • need further studies DIS Boros & Liang, PRD (1998). 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  12. Longitudinal polarization of H in • Relative better knowledge of helicity distributions of quarks in nucleon, in particular in relatively large x-region Further test of fragmentation function model • Different contributions from the fragmentation of quark of different flavors to different hyperons, e.g., +-polarization is more sensitive to u, - -polarization is more sensitive tod,  -polarization is more sensitive to s. Flavor separation of quark contributions to nucleon spin 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  13. The magnitude of P is small, and the decay influence is large! Longitudinal Polarization of Lambda SU(6) DIS Xu, Liu & Liang, PRD (2002) 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  14. Longitudinal Polarization of other hyperons Xu, Liu & Liang, PRD (2002) 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  15. Contributions from (A) dominate! A nice feature for  production in pp collisions from u-fragmentation first rank contributions from s-fragmentation A new and practical way to study polarized parton distributions. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  16. Transverse polarization of H in Study • Transversity distributions in nucleon • Spin-dependence of fragmentation functions in transversely polarized case little data available yet. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  17. Transverse polarization polarization direction the equal angle  • direction • magnitude scattering plan Polarization transfer in direction (helicity frame) magnitude real function of y 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  18. Transversely Polarized Case: Polarization of the scattered quark 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  19. obtained by assuming Transverse polarization of + A new way to study transversity at RHIC. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  20. Spin structure of nucleon sea: Anti-hyperon polarization in should be sensitive to helicity distributions of the anti-quarks in nucleon a complementary study of the spin structure of nucleon sea How much have we learned from inclusive and semi-inclusive DIS data? 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  21. Inclusive DIS data (polarized) HERMES, Phys. Rev. D 75 (2007) 山东大学(Shandong University), 梁作堂(Liang Zuo-tang) K. Rith 27

  22. Parton Model: Extracting  from Inclusive DIS data Integrated over x: Operator expression: SUf(3) Symmetry in Hyperon Decay Wigner-Eckart Theorem: E.g.: and 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  23. Polarized inclusive DIS  = 0.330 ± 0.025(theo) ± 0.011(exp) ± 0.028(evol) U = 0.842 ± 0.004(theo) ± 0.008(exp) ± 0.009(evol) D = - 0.427 ± 0.004(theo) ± 0.008(exp) ± 0:009(evol) S = - 0.085 ± 0.013(theo) ± 0.008(exp) ± 0.009(evol) HERMES, Phys. Rev. D 75 (2007) do not distinguish between q and q-bar: 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  24. Parton Model with QCD x-Dependence: The “QCD Analysis” (NLO) polarized Wilson coefficients, calculable in pQCD Inclusive DIS data on g1or A1 Empirical forms of q and g Spin-dependent parton distributions 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  25. NLO Results at Q2=4GeV2 The “QCD Analysis” of inclusive DIS data Blümlein & Böttcher, NPB636(02)225. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  26. A more direct measurement Flavor tagging in semi-inclusive DIS purity, spin independent, calculable using e.g. LEPTO. Separation of, not only flavors, but also quark and anti-quark. 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  27. Semi-inclusive DIS HERMES, PRL 92 (04) 012005, PRD 71 (05) 012003 (1) S = 0.037  0.019  0.027 c.f.: inclusive data and SU(3): S = - 0.085  0.013 0.012 (2) ? needs further studies, complementary measurements x 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  28. Anti-hyperon polarization in GRV00(valence) GRV00(standard) Xu, Liang, Sichtermann, PRD 2006 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  29. Anti-hyperon polarization in GRV00(valence) GRV00(valence) GRV00(standard) GRV00(standard) GRV00(valence) GRV00(valence) GRV00(valence) GRV00(standard) GRV00(standard) GRV00(standard) Chen, Liang, Sichtermann, Xu, Zhou, PRD 2008 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  30. An unique place to study spin-orbital interaction in QCD. Another window looking at the properties of QGP. ........................... Global polarization in AA collisions 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  31. Global Orbital Angular Momentum Huge orbital angular momentum of the colliding system reaction plan Y 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  32. Global orbital angular momentum Gradients in pz-distribution along x-direction 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  33. has a preferred direction ( ) ! impact parameter of the two partons Local Orbital Angular Momentum for b =RA, x=1fm 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  34. Local Orbital Angular Momentum Question: Can such local orbital angular momentum be transferred to the polarization via interaction between the partons due to the spin-orbital interaction in QCD, if a strongly interacting QGP is produced? 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  35. Quark scattering with fixed reaction plane Scattering amplitude in momentum space a 2-dimensional Fourier transformation to impact parameter space reaction plane , i: spin of the scattered quark Differential cross section w.r.t. the impact parameter average over the preferred directions un-polarized spin dependence Quark polarization: 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  36. Qualitative results Static potential model with “small angle approximation” Bessel functions spin direction of the quark after the scattering Liang and Wang, PRL(2005) QCD at finite temperature with HTL(hard thermal loop) gluon propagator scalar functions of xT Gao, Chen, Deng, Liang, Wang and Wang, PRC(2008) Both have exactly the same form ! 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  37. A new picture of QGP in non-central AA collisions The scattered quark acquires a negative polarization in the normal direction of the reaction plane! 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  38. Numerical results obtained using QCD at finite temperature LHC Landau fireball model RHIC More significant at LHC Gao, Chen, Deng, Liang, Wang and Wang, PRC(2008) 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  39. Lambda polarization STAR measurements Ilya Selyuzhenkov for STAR: QM2005; SQM2006; CIPANP 2006;QM2006; Xi’An 2006; STAR Paper, Phys.Rev.C76:024915,2007. arXiv:0705.1691 [nucl-ex] 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  40. Vector meson spin alignment STAR measurements • J. Chen for STAR, QM2006, J.Phys.G34:S331-S336,2007. • Z. Tang for STAR, Xi’An 2006. High Ener. Phys. & Nucl. Phys. • STAR Paper, 0801.1927[Nucl-ex] 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

  41. RHIC provides an unique place for hyperon polarization physics. Interesting physics can be learned from hyperon/anti-hyperon polarization measurements at RHIC, both in pp and AA collisions. Summary • spin-dependence of fragmentation function • spin structure of nucleon, sea structure and transversity • global polarization and spin-orbital interaction in QCD Thanks for your attention! 山东大学(Shandong University), 梁作堂(Liang Zuo-tang)

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