The study of $K^{\ast 0}$ meson production using a multi-phase transport model at RHIC BES energies

Abstract

We present the yield, average transverse momentum, and collective flow measurement of $K^{\ast 0}$ resonances in Au+Au collisions at $\sqrt{s_{NN}}=19.6$, 14.5, and 7.7~GeV using the AMPT model. It is found that, due to hadronic rescattering, the decay daughters of $K^{\ast 0}$ interact with other particles in the medium, causing the yield of reconstructable $K^{\ast 0}$ to be significantly suppressed, especially at low transverse momentum. The model results are compared with recent experimental data from Phase-II of the Beam Energy Scan (BES-II) program at the Relativistic Heavy-Ion Collider. The string-melting version of the AMPT model successfully reproduces the measured $K^{\ast 0}/K$ ratios at all three analysed collision energies. Interestingly, AMPT calculations that exclude the hadronic phase nevertheless provide a reasonable description of the data, thereby challenging the conventional interpretation that hadronic rescattering is the primary mechanism responsible for suppressing the $K^{\ast 0}/K$ ratio in central heavy-ion collisions. In addition, we find that the $K^{\ast 0}/K$ ratio appears to be largely insensitive to the lifetime of the hadronic phase, whereas the average transverse momentum, $⟨p_T⟩$, of the $K^{\ast 0}$ shows a strong dependence, increasing significantly as the lifetime of the hadronic phase becomes longer. We further show that the directed flow ($v_1$) of $K^{\ast 0}$ mesons is strongly influenced by hadronic rescattering, whereas the elliptic flow ($v_2$) exhibits only weak sensitivity to hadronic effects. These results establish $K^{\ast 0}$ directed flow as a sensitive probe of the late-stage hadronic medium in heavy-ion collisions. These model calculations therefore provide valuable insight into the underlying physics governing the observed experimental results at RHIC.

Comments: 9 pages, 11 figures