[论文解读] FASTSUM Generation 2L Anisotropic Thermal Lattice QCD Gauge Ensembles

Gert Aarts, Chris Allton+8 more|arXiv (Cornell University)|Sep 29, 2022

High-Energy Particle Collisions Research被引用 13

一句话总结

本研究利用包含 Nf=2+1 动态夸克的各向异性格点 QCD，在强子相中研究了开放粲介子（D 和 Ds）的热行为。通过分析无需谱重建的介子相关函数比值，发现赝标量和矢量 D 介子在穿越转变附近仅表现出约 1% 的质量降低，而标量和轴矢量态在整个强子相中表现出强烈的温度依赖性，表明存在超出简单质量移动的显著热效应。

ABSTRACT

FASTSUM Generation 2L Anisotropic Thermal Lattice QCD Gauge Ensembles The FASTSUM collaboration [1] Generation 2L Ensembles are lattice Quantum Chromodynamics (QCD) gauge-ensembles used extensively to examine thermal (non-zero temperature) properties of QCD using the first principles methods of lattice QCD. These are anisotropic lattices using the `fixed-scale` approach to thermal ensembles wherein the temperature is changed entirely by changing the number of points in the temporal direction. These ensembles have a quark mass closer to physical than our earlier Generation 2 Ensembles. These ensembles are available (see below) for non-competing research. The requirements of this use are that this Zenodo page, and the two papers detailing the ensembles, Properties of the QCD thermal transition with Nf=2+1 flavors of Wilson quark and Open charm mesons at nonzero temperature: results in the hadronic phase from lattice QCD are appropriately cited. These ensembles are characterised by \(N_f = 2 +1 \) flavour Degenerate up and down quarks, approximately physical strange quark spatial lattice spacing \(a_s\) ~0.112 fm temporal lattice spacing \(a_t\) ~0.033 fm anisotropy \( u = a_s / a_t\) ~3.453 Number of spatial sites NS NS = 32 Number of Temporal sites NT in [8, 128] Temperatures 47 MeV to 760 MeV Pseudocritical temperature (from renormalised chiral condensate) 167(3) MeV Pion mass \(m_\pi \sim 239\) MeV This choice action and bare parameters follows that of the Hadron Spectrum Collaboration https://doi.org/10.1103/PhysRevD.78.054501, namely a Symanzik improved gauge action and a tadpole improved Wilson-clover fermion action with stout-smeared links. The main parameters in the lattice action are listed below. The bare fermion anisotropy \(\gamma_f\) is obtained by \(\gamma_f = \gamma_g / u\). Full details may be found in Properties of the QCD thermal transition with Nf=2+1 flavors of Wilson quark and Open charm mesons at nonzero temperature: results in the hadronic phase from lattice QCD which are also attached to this record. gauge coupling \(\beta = 1.5\) tree-level coefficients \(c_0 = 5/3,\, c2=-1/12\) bare gauge, fermion anisotropy \(\gamma_g = 4.3,\, \gamma_f = 3.399\) ratio of bare anisotropies \( u = \gamma_g / \gamma_f = 1.265\) spatial tadpole (without, with smeared links) \(u_s = 0.733566, ilde{u}_s = 0.92674\) temporal tadpole (without, with smeared links) \(u_ au =1, ilde{u}_ au =1\) stout smearing for spatial links isotropic, 2 steps, \( ho = 0.14\) bare light quark mass \(m_0^l = -0.0860\) bare strange quark mass \(m^s_0 = -0.0743\) light quark hopping parameter \(\kappa_{light} = 0.27831\) strange quark hopping parameter \(\kappa_{strange} = 0.2765\) The available ensembles are detailed in the below table \(N_ au\) 128 64 56 48 40 36 32 28 24* 20* 16* 12 8 \(T\) MeV 47 95 109 127 152 169 190 217 253 304 380 507 760 \(T / T_{c}\) 0.284 0.569 0.650 0.758 0.910 1.011 1.138 1.300 1.517 1.820 2.275 3.034 4.550 \(N_{cfg}\) 1024 1041 1042 1123 1102 1119 1090 1031 1016 1030 1102 1267 1048 The ensembles marked by * also have ~100 configurations at \(N_S = 48\). Sharing & Usage The ensembles are currently available for non-competing research. To enquire, please contact (preferably) the generic email address PhysicsByFASTSUM AT gmail DOT com or one of Chris Allton or Jon-Ivar Skullerud. If they are used, this Zenodo page and two papers detailing the ensembles, Properties of the QCD thermal transition with Nf=2+1 flavors of Wilson quark and Open charm mesons at nonzero temperature: results in the hadronic phase from lattice QCD must be appropriately cited, i.e. with bibtex @article{PhysRevD.105.034504, title = {Properties of the QCD thermal transition with ${N}_{f}=2+1$ flavors of Wilson quark}, author = {Aarts, G. and Allton, C. and Glesaaen, J. and Hands, S. and J\"ager, B. and Kim, S. and Lombardo, M. P. and Nikolaev, A. A. and Ryan, S. M. and Skullerud, J.-I. and Wu, L.-K.}, journal = {Phys. Rev. D}, eprint = "2007.04188", archivePrefix = "arXiv", primaryClass = "hep-lat", volume = {105}, issue = {3}, pages = {034504}, numpages = {12}, year = {2022}, month = {Feb}, publisher = {American Physical Society}, doi = {10.1103/PhysRevD.105.034504}, url = {https://link.aps.org/doi/10.1103/PhysRevD.105.034504}} and @article{Aarts:2022krz, author = {Aarts, Gert and Allton, Chris and Bignell, Ryan and Burns, Timothy J. and Garc\'\i{}a-Mascaraque, Sergio Chaves and Hands, Simon and J\"ager, Benjamin and Kim, Seyong and Ryan, Sin\'ead M. and Skullerud, Jon-Ivar}, title = "{Open charm mesons at nonzero temperature: results in the hadronic phase from lattice QCD}", eprint = "2209.14681", archivePrefix = "arXiv", primaryClass = "hep-lat", month = "9", year = "2022"} [1] https://fastsum.gitlab.io/

研究动机与目标

• 利用第一性原理的格点 QCD 模拟，研究开放粲介子（D 和 Ds）在强子相中的热响应。
• 确定是否可在无需谱函数重建或拟合程序的情况下捕捉 D 介子基态质量的温度效应。
• 通过与强子相中非微扰格点结果的比较，为有效强子模型提供基准。
• 评估使用相关函数比值作为热 QCD 中谱函数变化代理的可行性。
• 通过重夸克-轻夸克介子中的质量劈裂与简并性模式，检验手征对称性恢复的前兆。

提出的方法

• 本研究使用涵盖五个温度的各向异性 Nf=2+1 量 flavour 格点 QCD 规范组集，覆盖强子相。
• 采用一种新方法，基于介子两点相关函数的比值，无需谱函数重建或拟合即可推断热质量移动。
• 通过结合校正赤池信息准则（AICc）的模型选择与拟合窗口内加权平均的稳健统计程序提取基态质量。
• 最终的基态质量估计值通过所有拟合窗口结果组合样本的中位数计算得出，使用四分位距（IQR）准则剔除异常值。
• 通过自 resampling 估计系统误差，物理质量通过将格点间距误差与回归误差的平方和开方获得。
• 该方法通过在不同初始和最终时间片（τ₀, τf）及多个 p 值（0.8, 0.9, 1.0）的 Nτ/2 下使用一致且自动化的程序，避免了人工选择拟合窗口。

实验结果

研究问题

• RQ1 D 和 Ds 介子的基态质量在强子相中随温度升高如何演化？
• RQ2 在无需谱函数重建或拟合的情况下，D 介子相关函数的热效应能在多大程度上被捕捉？
• RQ3 赝标量/矢量通道中的热效应是否与简单质量移动一致，还是暗示更深层次的动力学？
• RQ4 标量和轴矢量 D 介子是否表现出强烈的热效应，可能作为手征对称性恢复前兆？
• RQ5 在无谱函数重建的情况下，相关函数比值方法能否可靠提取热质量移动？

主要发现

• 在赝标量和矢量通道中，D 介子基态质量的热效应在百分之一量级，且与接近热交叉转变时基态质量平滑降低一致。
• 标量和轴矢量 D 介子通道在整个强子相中表现出显著的热效应，表明存在超出简单质量移动的强烈修正。
• 相关函数比值方法成功捕捉了热质量移动，无需谱函数重建或额外拟合，验证了其作为谱函数变化可靠代理的有效性。
• 基于 AICc 加权模型平均与 IQR 异常值剔除的中位数估计的基态质量提取程序，在不同拟合窗口下均产生稳定且系统的结果。
• 该方法表明标量和轴矢量 D 介子比赝标量和矢量态对热效应更敏感，提示这些通道中可能存在手征对称性恢复的信号。
• 本研究为有效强子模型提供了第一性原理基准，特别是在格点 QCD 模拟不可行的 QCD 相图区域。