Spin-Alignment of Vector Mesons in Relativistic Heavy-Ion Collisions

Abstract

In the present study, we explore the spin alignment of ρ, ϕ, and K∗0 vector mesons assuming the quarks (and anti-quarks) are polarized in the relativistic heavy-ion collisions. The initial orbital angular momentum imparted in the system due to the colliding nuclei helps to polarize the quarks in the medium and these quark-polarization is inherited to the hadron polarization. We explore the effect of external magnetic field eB and medium momentum-space anisotropy ξ on the spin-alignment of these vector mesons through the diagonal elements of the spin-density matrix ρ<inf>00</inf>. We consider two distinct hadronization processes: quark recombination and fragmentation to investigate this effect. Our findings reveal that is inversely related to medium anisotropy and directly related to the strength of the magnetic field, providing a qualitative explanation for the experimental data observed. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.