Global Polarization of Ξ and Ω Hyperons in Au plus Au Collisions at √SNN=200 GeV

作者：Adam, J.; Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I; Anderson, D. M.; Aparin, A.; Aschenauer, E. C.; Ashraf, M. U.; Atetalla, F. G.; Attri, A.; Averichev, G. S.; Bairathi, V; Barish, K.; Behera, A.; Bellwied, R.; Bhasin, A.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Brandenburg, J. D.; Brandin, A., V; Butterworth, J.; Caines, H.; Sanchez, M. Calderon de la Barca; Cebra, D.; Chakaberia, I; Chaloupka, P.; Chan, B. K.

来源：Physical Review Letters, 2021, 126(16): 162301.

DOI：10.1103/PhysRevLett.126.162301

• LAMBDA

Global polarization of Xi and Omega hyperons has been measured for the first time in Au + Au collisions at root S-NN= 200 GeV. The measurements of the Xi(-) and (Xi) over bar (+) hyperon polarization have been performed by two independent methods, via analysis of the angular distribution of the daughter particles in the parity violating weak decay Xi -> Lambda + pi, as well as by measuring the polarization of the daughter A hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over Xi(-) and (Xi) over bar (+), is measured to be < P-Xi > = 0.47 +/- 0.10(stat) +/- 0.23(syst)% for the collision centrality 20%-80%. The < P-Xi > is found to be slightly larger than the inclusive Lambda polarization and in reasonable agreement with a multiphase transport model. The < P-Xi > is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of Omega, < P-Omega > = 1.11 +/- 0.87(stat) +/- 1.97(syst)% was obtained by measuring the polarization of daughter Lambda in the decay Omega -> Lambda + K, assuming the polarization transfer factor C-Omega Lambda = 1.