Improved quark coalescence model for spin alignments of vector mesons

TL;DR

This paper introduces an improved quark coalescence model incorporating phase space dependence to better understand spin alignments of vector mesons, aligning with experimental observations.

Contribution

It presents a novel quark coalescence model that accounts for phase space, explaining spin alignment deviations of vector mesons from prior models.

Findings

Large positive deviation of ρ₀₀ for φ mesons from 1/3 due to electric field effects.

Negative deviation of ρ₀₀ for K*⁰ mesons linked to vorticity fields.

At low p_T, ρ₀₀ for K*⁰ scales with p_T², matching experimental data.

Abstract

We propose an improved quark coalescence model for spin alignment of vector mesons by spin density matrix with phase space dependence. Within this model we propose an understanding of spin alignments of vector mesons $\phi$ and $K^{*0}$ in the static limit: a large positive deviation of $\rho_{00}$ for $\phi$ mesons from $1/3$ may come from the electric part of the vector $\phi$ field, while a negative deviation of $\rho_{00}$ for $K^{*0}$ mesons may come from the electric part of vorticity fields. In the low-$p_T$ region, $\rho_{00}$ for $K^{*0}$ mesons is proportional to $p_T^2$, which is qualitatively agree with experimental results.