Speaker
Description
In non-central heavy-ion collisions, a large orbital angular momentum is produced. A part of the orbital angular momentum can polarize the quarks and anti-quarks, hence the vector mesons, inside the medium. Recently, STAR measured the global spin alignment of ϕ(1020) and K∗ (892) mesons in Au+Au collisions from the RHIC Beam Energy Scan I (BES I) program [1]. The global spin alignment, quantified by the 00th coefficient of the spin density matrix, ρ00, is measured by a fit to the acceptance and efficiency corrected ϕ meson yield versus polar angle (θ∗) between the daughter kaon in the parent’s rest frame and the orbital angular momentum direction. In this talk, we present an alternative approach to extract ρ00 by utilizing the ⟨cos2θ∗⟩ as a function of pair-invariant mass instead of analyzing the ϕ meson yields in cos θ∗ bins. We use a data-driven method to correct for acceptance and efficiency. We report new analysis from this method.
[1] M. Abdallah et al. (STAR Collaboration), Nature 614, 244–248 (2022).
