Speaker
Description
Directed flow $v_1$ has been used to probe the early dynamics in high-energy nuclear collisions. The vector meson $\phi(s\bar{s})$, with a mass comparable to that of light baryons and weak hadronic interactions, provides a unique probe of the interplay between particle production mechanisms and early-stage dynamics in high-density nuclear matter.
In this talk, we report measurements of $\phi$-meson directed flow ($v_1$) in Au+Au collisions at center-of-mass energies of 3.0, 3.2, 3.5, 3.9, and 4.5~GeV, using data collected by the STAR experiment as part of the RHIC Beam Energy Scan II program. These energies correspond to the high-baryon-density region of the QCD phase diagram, with baryon chemical potentials of $\mu_B \approx 590$--$760$~MeV. In this region, the measured $\phi$-meson $v_1$ exhibits a positive slope with a magnitude comparable to those of baryons, such as protons and $\Lambda$, while the directed flow of lighter mesons, including pions and kaons, is significantly smaller. The results are compared with UrQMD transport model calculations, providing insights into the role of baryon-resonance contributions and strange-hadron transport in dense QCD matter.
| Academic Status | I am a Ph.D. student |
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