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arXiv · 2505.06522

Phenomenology of baryon dynamics with directed flow in relativistic heavy-ion collisions

Tribhuban Parida
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Abstract

This thesis aims to elucidate the role of initial baryon stopping and its diffusion in heavy-ion collisions (HIC) using hydrodynamic model. In this regard, we have studied the observable-directed flow ($v_1$) of identified hadrons, particularly the $v_1$ of baryons and antibaryons, as well as the splitting observed between them in detail. We propose a new ansatz for the initial baryon distribution. By employing this initial baryon deposition model alongside a tilted energy distribution as inputs to a hybrid framework, we successfully describe the rapidity-odd $v_1$ of identified hadrons, including the elusive baryon-antibaryon splitting of $v_1$ across a wide range of $\sqrt{s_{NN}}$. Our model, incorporating baryon stopping and it's subsequent diffusion within a relativistic hydrodynamic framework and employing a crossover equation of state derived from lattice QCD calculations, establishes a non-critical baryonic baseline. Moreover, we demonstrate that recent STAR measurements of the centrality and system-size dependence of $v_1$ splitting between oppositely charged hadrons-attributed to electromagnetic field effects-are significantly influenced by background contributions from baryon stopping and its diffusion. Furthermore, we show that the rapidity dependence of the splitting of the rapidity-even component of $v_1$ between $p$ and $\bar{p}$ is highly sensitive to the initial baryon deposition scheme. If measured experimentally, this could constraint the rapidity dependence of the initial baryon deposition profile. Moreover, it could offer valuable phenomenological insights into the baryon junction picture and help refine constraints on the baryon diffusion coefficient of the medium. Notably, utilizing this phenomenologically successful baryon deposition model, we present the first estimation of the baryon diffusion coefficient for the strongly interacting QCD matter created in HIC.

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Tribhuban Parida. 2025-05-10. Phenomenology of baryon dynamics with directed flow in relativistic heavy-ion collisions. https://arxiv.org/abs/2505.06522

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