New insights into global spin alignment of vector mesons using relativistic heavy-ion collisions from STAR

Fudan University, 220 Handan Rd., Yangpu District, Shanghai ( 200433), CHINA

^* e-mail: xibaoshan@fudan.edu.cn
^** Besides the acknowledgements to STAR Collaboration, we wish to thank the NSFC under contract No. 12025501 for contributing to the local expenses.

Published online: 26 June 2024

Abstract

In these proceedings, we present new measurements from STAR of the global spin alignment(ρ₀₀) of ϕ mesons in Au+Au collisions at √S_NN = 19.6, 14.6 GeV using BES-II data and of J/ψ mesons in isobar collisions ₄₄⁹⁶Ru + ₄₄⁹⁶Ru and ₄₀⁹⁶Zr + ₄₀⁹⁶Zr at √S_NN = 200 GeV. The energy-dependent spin alignment for ϕ mesons from BES-II data is consistent with that published from BES-I and showcases a significant improvement in precision. We performed a new measurement assessing the rapidity dependence of ϕ meson ρ₀₀, and our findings are consistent with theoretical predictions. The global spin alignment of J/ψ mesons with respect to first order event plane aligns with a value of 1/3 within the statistical error. Additionally, we discuss the procedure of measuring the global spin alignment of ρ⁰ mesons at RHIC and provide the projection for errors.