标题： 夸克-胶子等离子体在不同阶段的温度测量 显示英文标题

标题： Temperature Measurement of Quark-Gluon Plasma at Different Stages

摘要： 在夸克-胶子等离子体（QGP）中，物质的基本组成单元——夸克和胶子，在极端的温度和密度条件下存在。 QGP可能存在于宇宙的早期阶段，以及宇宙中的各种天体和事件中。 QGP的热力学和流体力学性质由量子色动力学（QCD）描述，并可以在重离子碰撞中进行研究。 尽管是关键的热力学参数，QGP的温度仍然知之甚少。 热轻子对（$e^+e^-$和$\mu^+\mu^-$）是探测发射源真实温度的理想穿透探针，因为它们的不变质量谱既不受强末态相互作用的影响，也不受快速膨胀引起的蓝移效应的影响。 在此，我们通过相对论重离子对撞机（RHIC）中的热$e^+e^-$产生来测量QGP温度。 低质量区域（介质中$\rho^0$向量介子占主导）的平均温度为$(1.99 \pm 0.24) \times 10^{12}$K，与统计模型中的化学冻结温度和LQCD中的相变温度一致。 中间质量区域（高于$\rho^0$质量，QGP占主导）的平均温度显著更高，为$(3.40 \pm 0.55)\times 10^{12}$K。这项工作提供了绘制QCD相图并理解极端条件下物质性质的重要实验热力学测量数据。 显示英文摘要

摘要： In a Quark-Gluon Plasma (QGP), the fundamental building blocks of matter, quarks and gluons, are under extreme conditions of temperature and density. A QGP could exist in the early stages of the Universe, and in various objects and events in the cosmos. The thermodynamic and hydrodynamic properties of the QGP are described by Quantum Chromodynamics (QCD) and can be studied in heavy-ion collisions. Despite being a key thermodynamic parameter, the QGP temperature is still poorly known. Thermal lepton pairs ($e^+e^-$ and $\mu^+\mu^-$) are ideal penetrating probes of the true temperature of the emitting source, since their invariant-mass spectra suffer neither from strong final-state interactions nor from blue-shift effects due to rapid expansion. Here we measure the QGP temperature using thermal $e^+e^-$ production at the Relativistic Heavy Ion Collider (RHIC). The average temperature from the low-mass region (in-medium $\rho^0$ vector-meson dominant) is $(1.99 \pm 0.24) \times 10^{12}$ K, consistent with the chemical freeze-out temperature from statistical models and the phase transition temperature from LQCD. The average temperature from the intermediate mass region (above the $\rho^0$ mass, QGP dominant) is significantly higher at $(3.40 \pm 0.55)\times 10^{12}$ K. This work provides essential experimental thermodynamic measurements to map out the QCD phase diagram and understand the properties of matter under extreme conditions.