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arXiv 2407.01657hep-lat
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手征交叉区域附近的热QCD物质:基于O(a)改进Wilson费米子的格点研究

Hot QCD matter around the chiral crossover: a lattice study with $O(a)$-improved Wilson fermions

Ardit Krasniqi, Marco Cè, Renwick J. Hudspith, Harvey B. Meyer

AI总结:

本文通过格点QCD模拟研究手征交叉附近热QCD物质,发现π介子准粒子随温度升高变轻且极点变为扩散型,并揭示矢量与轴矢量谱函数的热修正及手征序参量被显著抑制。

摘要:

利用带有O(a)改进的Wilson夸克以及物理上、下和奇异夸克质量的格点QCD模拟,我们在固定格距a=0.064 fm、体积V=(6.1 fm)^3的条件下,研究了温度T={128,154,192} MeV时热QCD物质的性质。我们发现,定义为轴电荷两点函数中低能极点的π介子准粒子随着温度升高而变轻,并基于流体动力学给出论证,说明为什么该极点在高于手征交叉温度后变为纯扩散型。我们使用Backus-Gilbert方法研究了同位旋矢量矢量谱函数的热修正,发现低能区增强而约1 GeV能量附近减弱。对轴矢量通道的类似研究揭示了在低于1 GeV能量处更大的增强,并且我们证明这些发现与严格的谱求和规则一致。矢量与轴矢量关联函数之差是手征对称性的序参量,结果表明它在交叉区域整体被抑制超过一个数量级。

英文摘要:

Using lattice QCD simulations with $O(a)$-improved Wilson quarks and physical up, down and strange quark masses, we investigate the properties of thermal QCD matter at the temperatures $T=\{128,154,192\}\mathrm{MeV}$ with a fixed lattice spacing $a=0.064\mathrm{fm}$ and volume $V=(6.1\text{fm})^3$. We find that the pion quasiparticle, defined as the low-energy pole in the two-point function of the axial charge, becomes lighter as the temperature increases and give an argument based on hydrodynamics as to why the pole becomes purely diffusive above the chiral crossover. We study the thermal modification of the isovector vector spectral function using the Backus-Gilbert method, finding an enhancement at low energies and a depletion at energies around $1\mathrm{GeV}$.The analogous study of the axial-vector channel reveals a larger enhancement at energies below $1\mathrm{GeV}$, and we show that these findings are consistent with rigorous spectral sum rules. The difference between vector and axial-vector correlators, an order parameter for chiral symmetry, turns out to be overall suppressed by more than an order of magnitude at the crossover.

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