STAR Paper Proposal

Measurements of global polarization of Lambda (anti-Lambda) and Xi- (Xi+) hyperons in isobar collisions at sqrt(s_NN) = 200 GeV

General information
Title: Measurements of global polarization of Lambda (anti-Lambda) and Xi- (Xi+) hyperons in isobar collisions at sqrt(s_NN) = 200 GeV 
Principal Authors: Xingrui Gou (Shandong), Takafumi Niida (Tsukuba), Sergei A. Voloshin (WSU), Zhenyu Chen (Shandong), Qinghua Xu (Shandong)
Target Journal: PRL
GPC members:

Abstract

Global polarization of Lambda (anti-Lambda) and Xi- (Xi+) hyperons has been measured in isobar Ru+Ru and Zr+Zr collisions at sqrt(s_NN) = 200 GeV recorded with STAR at RHIC. We report the measurements for different collision centralities, and the Lambda (anti-Lambda)  results in 20-60% centrality interval as functions of pT and eta. No significant difference has been observed between the results of Lambda and anti-Lambda. The results increase towards peripheral collisions, with no significant p_T or η dependence. Comparison to the results in Au+Au collisions at sqrt(s_NN) = 200 GeV reveals no obvious system size dependence.

Proposed figures

Figure1

Fig.1:Polarization of Λ+anti-Λ as a function of centrality in Ru+Ru and Zr+Zr collisions at sqrt(s_NN)=200 GeV. Open boxes and vertical lines show systematic and statistical uncertainties, respectively. Results for the Λ and anti-Λ measurements in Au+Au collisions at sqrt(s_NN)=200 GeV are shown for comparison.

Figure2

Fig.2 : Polarization of Λ+anti-Λ as a function of p_T for the 20%-60% centrality in Ru+Ru & Zr+Zr collisions at sqrt(s_NN)=200 GeV.  Open boxes and vertical lines show systematic and statistical uncertainties, respectively. Results for the Λ and anti-Λ measurements in Au+Au collisions at sqrt(s_NN)=200 GeV are shown for comparison.

Figure3

Fig.3 : P_{y,c0} and P_{y,c2} of Λ+anti-Λ as a function of centrality in Ru+Ru&Zr+Zr collisions at sqrt(s_NN)=200 GeV. Open boxes and vertical lines show systematic and statistical uncertainties, respectively.

Figure4

Fig.4 : The global polarization of Ξ-+Ξ+  hyperons obtained via measurements of the polarization of daughter Lambda hyperons and direct measurements as a function of the centrality bins in isobar collisions at sqrt(s_NN)=200 GeV. Results for Ξ-+Ξ+  in Au+Au collisions at sqrt(s_NN)=200 GeV are shown for comparison.