Reconstructability and directed flow of short-lived resonances in Au+Au collisions at 19.6 and 200 GeV

Abstract

We present a systematic study of the reconstructability and directed flow of hadronic resonances in Au+Au collisions within the UrQMD transport model. The main objective of this work is to investigate how the hadronic stage influences both resonance reconstructability and the final-state directed flow. A set of short-lived hadronic resonances, including $ρ^0$, $K^{*0}$, and $Λ(1520)$, is investigated to quantify their yields and reconstructable fractions as a function of charged-particle multiplicity, characterized by $(dN_{ch}/dη)^{1/3}$. We compare results at $\sqrt{s_{NN}} = 19.6$ and $200 ~\mathrm{GeV}$ to investigate possible energy-dependent differences in the reconstructability. Such differences reflect variations in the properties of the hadronic medium. The results are further examined as a function of resonance lifetime, revealing a clear ordering of reconstructability among different resonances. Overall, the reconstructability is found to be primarily governed by resonance lifetime. The directed-flow analysis reveals clear differences between resonances and their corresponding stable hadrons in mid-central collisions, while these differences become significantly weaker in peripheral collisions, highlighting the important role of hadronic evolution in shaping the final-state directed flow. These studies provide a unified picture of how the hadronic stage influences both resonance reconstructability and directed flow, offering new insights into resonance observables in relativistic heavy-ion collisions.