arXiv 2407.093352024-07hep-lathep-ph

(2+1)-味 QCD 赝临界线上的奇异数关联

Strangeness-Correlations on the pseudo-critical line in (2+1)-flavor QCD

D. Bollweg, H. -T. Ding, J. Goswami, F. Karsch, Swagato Mukherjee, P. Petreczky, C. Schmidt

备注：: 9 pages, 6 figures
发表信息：: Phys.Rev.D 110 (2024) 5, 054519

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AI总结：

本研究利用(2+1)-味格点QCD计算赝临界线上B、S、Q累积量与关联，并与RHIC/STAR实验数据比较，确定奇异数中性条件及冻出重子化学势。

摘要：

我们给出了关于(2+1)-味 QCD 的温度（T）—重子化学势（μ_B）相图中，沿赝临界线（T_pc(μ_B)）的净重子数（B）、奇异数（S）和电荷（Q）的一阶累积量（χ_1^i）、二阶累积量（χ_2^i）以及它们之间关联（χ_{11}^{ij}）的一些格点QCD结果。我们指出，在RHIC束流能量扫描所覆盖的整个μ_B范围内，沿T_pc(μ_B)，对电荷化学势为零这一同位旋对称极限的偏离很小。对于重离子碰撞中产生的奇异数中性物质，这导致χ_{11}^{BS}与χ_{11}^{QS}之间存在密切关系。我们将沿T_pc(μ_B)线的χ_{11}^{BS}/χ_2^S格点QCD结果，与碰撞能量7.7 GeV≤√s_NN≤62.4 GeV下χ_{11}^{BS}/χ_2^S的初步实验测量结果进行了比较。虽然我们发现在√s_NN≥39 GeV时符合良好，但在√s_NN较小值时差异相当大。此外，我们将奇异数化学势（μ_S）与重子化学势（μ_B）之比的格点QCD结果——该比值定义了具有固定电荷与重子数密度比的奇异数中性系统——与STAR合作组利用冻出线上的奇异重子产额获得的μ_S/μ_B实验结果进行了比较。最后，我们通过将沿T_pc(μ_B)的χ_1^B/χ_2^B与实验测量的净质子累积量χ_1^p/χ_2^p进行比较，确定了冻出时的重子化学势（μ_B^f）。我们发现，对于√s_NN≥11.5 GeV，{μ_B^f, T_pc(μ_B^f)}与对实验测量强子产额进行统计模型拟合所得的冻出参数一致。

英文摘要：

We present some lattice QCD results on first ($χ_1^i$) and second ($χ_2^i$) cumulants of and correlations ($χ_{11}^{ij}$) among net baryon-number ($B$), strangeness ($S$) and electric charge ($Q$) along the pseudo-critical line ($T_{pc}(μ_B)$) in the temperature ($T$)--baryon chemical potential ($μ_B$) phase diagram of (2+1)-flavor QCD. We point out that violations of the isospin symmetric limit of vanishing electric charge chemical potential are small along the $T_{pc}(μ_B)$ for the entire range of $μ_B$ covered in the RHIC beam energy scan. For the strangeness neutral matter produced in heavy-ion collisions this leads to a close relation between $χ_{11}^{BS}$ and $χ_{11}^{QS}$. We compare lattice QCD results for $χ_{11}^{BS}/χ_2^S$ along the $T_{pc}(μ_B)$ line with preliminary experimental measurements of $χ_{11}^{BS}/χ_2^S$ for collision energies $7.7~{\rm GeV}\le \sqrt{s_{_{NN}}}\le 62.4~{\rm GeV}$. While we find good agreements for $\sqrt{s_{_{NN}}}\ge 39$~GeV, differences are sizeable at smaller values of $\sqrt{s_{_{NN}}}$. Moreover, we compare lattice QCD results for the ratio of the strangeness ($μ_S$) to baryon ($μ_B$) chemical potentials, which define a strangeness neutral system with fixed electric charge to baryon number density, with experimental results obtained by the STAR collaboration for $μ_S/μ_B$ using strange baryon yields on the freeze-out line. Finally, we determine the baryon chemical potential at the freeze-out ($μ_B^f$) by comparing $χ_1^B/χ_2^B$ along the $T_{pc}(μ_B)$ with the experimentally measured net-proton cumulants $χ_1^p/χ_2^p$. We find that $\{μ_B^f, T_{pc}(μ_B^f) \}$ are consistent with the freeze-out parameters of the statistical-model fits to experimentally measured hadron yields for $\sqrt{s_{_{NN}}} \geq 11.5$ GeV.

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