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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2603.28742 |
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| _version_ | 1866912989367500800 |
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| author | Bairathi, Vipul Nayak, Kishora |
| author_facet | Bairathi, Vipul Nayak, Kishora |
| contents | The directed flow ($v_1$) of identified hadrons ($π^{\pm}, K^{\pm}, p, \bar{p}, ϕ, Λ$, and $\barΛ$) is studied in symmetric nuclear collisions (O+O, Cu+Cu, Ru+Ru, Au+Au, and U+U) at $\sqrt{s_{NN}} = 200$ GeV using the string-melting version of a multiphase transport model with improved quark coalescence. The mid-rapidity $v_1$-slope ($dv_1/dy$) and its charge-dependent splitting ($Δdv_1/dy$) between particles and anti-particles are investigated as a function of nuclear mass number ($A$) and collision centrality in both low-$p_\mathrm{T}$ (0.2$-$2.0 GeV/$c$) and high-$p_\mathrm{T}$ (2.0$-$5.0 GeV/$c$) regions. At low-$p_\mathrm{T}$, the $v_1$-slope shows weak system-size dependence, while at high-$p_\mathrm{T}$ strong system-size dependence is found and it becomes negative with nuclear mass number, reflecting the hard-soft asymmetry in particle production. The charge-dependent splitting $Δdv_1/dy$ reveals a striking baryon-meson dichotomy: baryon pairs ($p-\bar{p}$ and $Λ-\barΛ$) exhibit significant splitting that grows with system size, whereas meson pairs ($π^+-π^-$ and $K^+-K^-$) show minimal splitting. The effect of final state hadronic interactions on the $v_1$-slope is found to be negligible confirming that it is primarily generated during the partonic phase and coalescence process. A comparison of the AMPT results with measurements from the STAR experiment at RHIC in Au+Au collisions establish the transported quark contribution as a baseline for the observed charge-dependent $v_1$ splitting, on top of which electromagnetic field effects must be considered. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_28742 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Charge-Dependent Directed Flow in Symmetric Nuclear Collisions Bairathi, Vipul Nayak, Kishora High Energy Physics - Phenomenology Nuclear Theory The directed flow ($v_1$) of identified hadrons ($π^{\pm}, K^{\pm}, p, \bar{p}, ϕ, Λ$, and $\barΛ$) is studied in symmetric nuclear collisions (O+O, Cu+Cu, Ru+Ru, Au+Au, and U+U) at $\sqrt{s_{NN}} = 200$ GeV using the string-melting version of a multiphase transport model with improved quark coalescence. The mid-rapidity $v_1$-slope ($dv_1/dy$) and its charge-dependent splitting ($Δdv_1/dy$) between particles and anti-particles are investigated as a function of nuclear mass number ($A$) and collision centrality in both low-$p_\mathrm{T}$ (0.2$-$2.0 GeV/$c$) and high-$p_\mathrm{T}$ (2.0$-$5.0 GeV/$c$) regions. At low-$p_\mathrm{T}$, the $v_1$-slope shows weak system-size dependence, while at high-$p_\mathrm{T}$ strong system-size dependence is found and it becomes negative with nuclear mass number, reflecting the hard-soft asymmetry in particle production. The charge-dependent splitting $Δdv_1/dy$ reveals a striking baryon-meson dichotomy: baryon pairs ($p-\bar{p}$ and $Λ-\barΛ$) exhibit significant splitting that grows with system size, whereas meson pairs ($π^+-π^-$ and $K^+-K^-$) show minimal splitting. The effect of final state hadronic interactions on the $v_1$-slope is found to be negligible confirming that it is primarily generated during the partonic phase and coalescence process. A comparison of the AMPT results with measurements from the STAR experiment at RHIC in Au+Au collisions establish the transported quark contribution as a baseline for the observed charge-dependent $v_1$ splitting, on top of which electromagnetic field effects must be considered. |
| title | Charge-Dependent Directed Flow in Symmetric Nuclear Collisions |
| topic | High Energy Physics - Phenomenology Nuclear Theory |
| url | https://arxiv.org/abs/2603.28742 |