Centrality dependence of hyperon global polarization in Au+Au collisions at RHIC

We present the centrality dependence of A and A hyperon global polarization in Au+Au collisions at √SNN = 62 GeV and 200 GeV measured with the STAR detector at RHIC. Within the precision of the measurement, we observe no centrality dependence of A and A hyperon global polarization, and within our acceptance it is consistent with zero. Different sources of systematic uncertainties (feed down effects, spin precession) are discussed and estimated. The obtained upper limit, | P Λ,Ā | ≤ 0.02, is compared to theoretical predictions discussed recently in literatures.

[1]  I. Selyuzhenkov.  Acceptance Effects in the Hyperons Global Polarization Measurement , 2006, nucl-ex/0608034.

[2]  Xin-Nian Wang,et al.  Erratum: Globally Polarized Quark-Gluon Plasma in NoncentralA+ACollisions [Phys. Rev. Lett.94, 102301 (2005)] , 2006 .

[3]  G. Buren.  The Σ0/Λ ratio in high energy nuclear collisions , 2005 .

[4]  Xiangzhou Cai.  Production of K0s, ϕ, Λ and Ξ from 200 GeV d+Au collisions at RHIC , 2005 .

[5]  Xin-Nian Wang,et al.  Spin alignment of vector mesons in non-central A+A collisions , 2004, nucl-th/0411101.

[6]  Xin-Nian Wang,et al.  Globally polarized quark-gluon plasma in noncentral A + A collisions. , 2004, Physical review letters.

[7]  J. Thomas,et al.  The STAR time projection chamber: a unique tool for studying high multiplicity events at RHIC , 2003, nucl-ex/0301015.

[8]  K. J. Foley,et al.  The forward time projection chamber in STAR , 2002, nucl-ex/0211014.

[9]  A.M.Poskanzer,et al.  Methods for analyzing anisotropic flow in relativistic nuclear collisions , 1998, nucl-ex/9805001.

[10]  E. al.,et al.  Energy and charged particle flow in 10.8A GeV/c Au+Au collisions , 1996, nucl-ex/9610006.

[11]  S. Voloshin,et al.  Flow study in relativistic nuclear collisions by Fourier expansion of azimuthal particle distributions , 1994, hep-ph/9407282.

[12]  M. Cha,et al.  POLARIZATION OF A DECAY PARTICLE IN A TWO-STEP PROCESS: APPLICATION TO K$sup -$ + p $Yields$ $pi$$sup 0$ + $Sigma$$sup 0$, $Sigma$$sup 0$ $Yields$ $gamma$ + $lambda$ , 1965 .

[13]  E. Kluge,et al.  K−p cross sections from440 to 800 MeV/c , 1970 .