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

摘要

We present the centrality dependence of Lambda and (Lambda) over bar hyperon global polarization in Au+Au collisions at root(NN)-N-S = 62 GeV and 200 GeV measured with the STAR detector at RHIC. Within the precision of the measurement, we observe no centrality dependence of Lambda and (Lambda) over bar 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, vertical bar P-Lambda,P-(Lambda) over bar vertical bar <= 0.02, is compared to theoretical predictions discussed recently in literatures.