Dileptons produced during heavy-ion collisions represent a unique probe of the QCD phase diagram, and convey information about the state of the strongly interacting system at the moment their preceding off-shell photon is created. In this study, we compute thermal dilepton yields from $\mathrm{Au}+\mathrm{Au}$ collisions performed at different beam energies, employing a ($3+1$)-dimensional dynamic framework combined with emission rates accurate at next-to-leading order in perturbation theory and which include baryon chemical potential dependencies. By comparing the effective temperature extracted from the thermal dilepton invariant mass spectrum with the average temperature of the fluid, we offer a robust quantitative validation of dileptons as an effective probe of the early quark-gluon plasma stage.

中文翻译：

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虚拟光子揭示了致密 QCD 物质的早期温度

重离子碰撞过程中产生的双轻子代表了 QCD 相图的独特探针，并传达了有关强相互作用系统在其前一个离壳光子产生时的状态信息。在这项研究中，我们计算热双轻子产率$金+金$在不同的光束能量下进行碰撞，采用（$3+1$) 维动态框架与微扰理论中精确到次领先的发射率相结合，其中包括重子化学势依赖性。通过将从热双轻子不变质谱中提取的有效温度与流体的平均温度进行比较，我们对双轻子作为早期夸克-胶子等离子体阶段的有效探针进行了稳健的定量验证。