A phenomenological approach to direct ${\rm{K}}^{*}$ production and hadronic medium effects in nucleus-nucleus collisions at high baryon density

Abstract

Short-lived hadron resonances serve as sensitive probes of the late-stage hadronic medium in heavy-ion collisions. Using the AMPT-HC model, we study ${\rm{K}}^{*}(892)$ production and its hadronic medium effects in Au+Au collisions at $\sqrt{s_{\rm{NN}}} = 3$ GeV, a region of high baryon density. We introduce a phenomenological direct-production mechanism for ${\rm K}^{*}$ by replacing a fraction of the final-state kaons produced in the ${\rm NN} \to {\rm NYK}$ and ${\rm MN} \to {\rm YK}$ channels with ${\rm K}^{*}$ resonances, with the substitution fraction controlled by a parameter $α$ while conserving four-momentum. The direct ${\rm K}^{*}$ is produced early, at about 6 fm/$c$, with little centrality dependence, whereas resonance fusion via ${\rm K}+π\to{\rm K}^{*}$ occurs later, with the mean production time increasing from about 8 to 10 fm/$c$ toward central collisions. Consequently, direct ${\rm K}^{*}$ mesons suffer stronger daughter rescattering, leading to a pronounced decrease in reconstruction efficiency toward central collisions, while the ${\rm K}^{*}$ survival rate remains close to unity. Elastic scattering of the daughters also shifts the invariant mass away from the resonance peak, contributing to the background-like component. The ${\rm K}^{*}/{\rm K}$ centrality dependence reflects the competition between direct production and resonance fusion and is sensitive to $α$. At 3 GeV, a moderate direct-production contribution may result in an increasing ${\rm K}^{*}/{\rm K}$ ratio toward central collisions, providing a testable prediction for future measurements.