QM abstract for oral presentation

Title : Measurement of directed flow of K* and φ Resonances in Au+Au collisions at RHIC BES energies

Author: Md Nasim (for the STAR collaboration)

It is known from earlier studies that the hadronic interaction affects the measured yield of short lived resonance e.g. K*⁰.  Recent study [1] shows that the directed flow (v₁) of K*⁰ is strongly affected during the hadronic stage due to asymmetric loss in different sides of the p_x axis in momentum space caused by the tilted fireball. Therefore the v₁ of K*⁰ can be a good probe to study the late-stage hadronic interaction and provide more information compared to the yield measurement integrated over full azimuth and rapidity. 
We present the first measurement of directed flow of K*⁰ resonances in Au+Au collisions at RHIC BES energies. Our measurement shows a centrality-dependent difference in directed flow between charged kaons and K*⁰ resonances, with this difference becoming more pronounced with increasing centrality. In contrast, the difference in directed flow between kaons and φ mesons remains nearly independent of centrality. The observed variation in directed flow between charged kaons and K*⁰ resonances can be qualitatively explained using a hydrodynamic model that incorporates a hadronic afterburner.  The measured v₁ of K*⁰ resonances can provide more insights into hadronic rescattering and regeneration processes in heavy-ion collisions and constrain transport- based models for QCD matter.

[1]  Phys. Rev. C 109, 044905 (2024)