The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions can produce strong magnetic fields on the order of ${10}^{18}\mathrm{G}$, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as $v_1(\mathsf{y})$. Here, we present the charge-dependent measurements of $d{v}_1/d\mathsf{y}$ near midrapidities for ${\pi }^{\pm }$, $K^{\pm }$, and $p(\overline{p})$ in $\mathrm{Au}+\mathrm{Au}$ and isobar (${}_{44}{}^{96}\mathrm{Ru}+{}_{44}{}^{96}\mathrm{Ru}$ and ${}_{40}{}^{96}\mathrm{Zr}+{}_{40}{}^{96}\mathrm{Zr}$) collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}$, and in $\mathrm{Au}+\mathrm{Au}$ collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the $v_1$ signal on collision system, particle species, and collision centrality can be qualitatively and semiquantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the $u$ and $d$ quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations.

中文翻译：

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在相对论性重离子对撞机上通过电荷相关定向流观测重离子碰撞中的电磁场效应

相对论性重离子碰撞中产生的解禁夸克胶子等离子体（QGP）使我们能够探索极端条件下物质的基本特性。非中心碰撞可以产生大约以下的强磁场：${10}^{18}\mathrm{G}$，它提供了对 QGP 电导率的探测。特别是，夸克和反夸克带有相反的电荷，并受到相反的电磁力，从而改变它们的动量。这种现象可以体现在终态粒子的集体运动中，特别是奇数速定向流中，表示为$v_1（\mathsf{y}）$。在这里，我们提出了电荷相关的测量$d{v}_1/d\mathsf{y}$接近中急流的${\pi }^{\pm }$,$K^{\pm }$， 和$p（\stackrel{￣}{p}）$在$金+金$和等压线（${}_{44}{}^{96}茹+{}_{44}{}^{96}茹$和${}_{40}{}^{96}锆+{}_{40}{}^{96}锆$) 碰撞$\sqrt{s_{\mathrm{神经网络}}}=200\mathrm{GeV}$，并在$金+金$相对论重离子对撞机的 STAR 探测器记录了 27 GeV 的碰撞。的综合依赖性$v_1$碰撞系统、粒子种类和碰撞中心性的信号可以定性和半定量地理解为对组成夸克的几种影响。虽然中心事件的结果可以解释为$你$和$d$从初始状态核传输的夸克，外围事件中的夸克揭示了电磁场对 QGP 的影响。我们的数据在理论计算中对 QGP 的电导率提出了有价值的限制。