Xin-Li Sheng, Lucia Oliva, Zuo-Tang Liang, Qun Wang, and Xin-Nian Wang, Spin Alignment of Vector Mesons in Heavy-Ion Collisions, Phys. Rev. Lett. 131, 042304 (2023)
Polarized quarks and antiquarks in high-energy heavy-ion collisions can lead to the spin alignment of vector mesons formed by quark coalescence. Using the relativistic spin Boltzmann equation for vector mesons derived from Kadanoff-Baym equations with an effective quark-meson model for strong interaction and quark coalescence model for hadronizaton, we calculate the spin density matrix element ρ00 for ϕ mesons and show that anisotropies of local field correlations with respect to the spin quantization direction lead to ϕ meson’s spin alignment. We propose that the local correlation or fluctuation of ϕ fields is the dominant mechanism for the observed ϕ meson’s spin alignment and its strength can be extracted from experimental data as functions of collision energies. The calculated transverse momentum dependence of ρ00 agrees with STAR’s data. We further predict the azimuthal angle dependence of ρ00 which can be tested in future experiments.
Figure: Contour plot of ρy00-1/3 for ϕ mesons as a function of kx and ky in 0%–80% Au+Au collisions at √sNN=200 GeV
See also: LBNL News Report
