Title: Chiral condensates and screening masses of neutral pseudoscalar mesons from lattice QCD at physical quark masses Show Chinese title

Title: 手征凝聚和中性伪标量介子的筛选质量从物理夸克质量的格点QCD

Abstract: We investigate the effects of temperature $T$ and external magnetic fields $eB$ on the chiral condensates and screening masses of neutral pseudoscalar mesons, including $\pi^0$, $K^0$, and $\eta_{s\bar{s}}^0$, in (2+1)-flavor lattice QCD with physical quark masses. The chiral condensates are intrinsically connected to the screening masses via Ward-Takahashi identities, with the latter characterizing the inverse of the spatial correlation length in the pseudoscalar channel. Using highly improved staggered quarks, we perform simulations on lattices with temporal extents $N_\tau = 8, 12, 16$ and an aspect ratio of 4, covering five temperatures from 145 MeV to 166 MeV. For each temperature, eight magnetic field strengths are simulated, reaching up to $eB \sim 0.8$ GeV$^2$. These simulations allow us to provide continuum estimates for the chiral condensates and screening masses. We observe intricate behavior in the light ($ud$), strange-light ($ds$) and strange ($s$) quark condensates as functions of the magnetic field and temperature, reflecting the competition between magnetic catalysis and inverse magnetic catalysis effects. This complex behavior is also mirrored in the screening masses of the neutral pseudoscalar mesons. Notably, the screening masses of $\pi^0$ and $K^0$ exhibit a non-monotonic dependence on $eB$, closely following the variations in their corresponding chiral condensates. Meanwhile, the screening mass of $\eta_{s\bar{s}}^0$ decreases monotonically with increasing $eB$. These findings provide valuable insights for understanding the behavior of QCD in a thermomagnetic medium and can serve as benchmarks for low-energy QCD models and effective theories. Show Chinese abstract

Abstract: 我们研究温度$T$和外部磁场$eB$对中性伪标量介子的手征凝聚和屏蔽质量的影响，包括$\pi^0$、$K^0$和$\eta_{s\bar{s}}^0$，在具有物理夸克质量的(2+1)-味格点QCD中。 手征凝聚通过Ward-Takahashi恒等式与屏蔽质量内在地联系在一起，后者表征了伪标量通道中空间相关长度的倒数。 使用高度改进的阶梯夸克，我们在时间扩展为$N_\tau = 8, 12, 16$且纵横比为4的格点上进行模拟，覆盖从145 MeV到166 MeV的五个温度。 对于每个温度，模拟了八种磁场强度，最高达到$eB \sim 0.8$ GeV$^2$。 这些模拟使我们能够为手征凝聚和屏敝质量提供连续估计。 我们观察到轻（$ud$）、奇-轻（$ds$）和奇（$s$）夸克凝聚随着磁场和温度的变化表现出复杂的特性，反映了磁催化效应和逆磁催化效应之间的竞争。 这种复杂的行为也体现在中性伪标量介子的屏敝质量中。 值得注意的是，$\pi^0$和$K^0$的筛选质量对$eB$表现出非单调的依赖关系，紧密跟随其相应的手征凝聚的变化。 同时，$\eta_{s\bar{s}}^0$的筛选质量随着$eB$的增加而单调减少。 这些发现为理解热磁介质中 QCD 的行为提供了有价值的见解，并可以作为低能 QCD 模型和有效理论的基准。