Insights on proton structure from lattice QCD: The twist-3 parton distribution function gT(x)

S. Bhattacharya, K. Cichy, M. Constantinou, A. Metz, Aurora Scapellato, F. Steffens
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引用次数: 21

Abstract

In this work, we present the first-ever calculation of the isovector flavor combination of the twist-3 parton distribution function $g_T(x)$ for the proton from lattice QCD. We use an ensemble of gauge configurations with two degenerate light, a strange and a charm quark ($N_f=2+1+1$) of maximally twisted mass fermions with a clover improvement. The lattice has a spatial extent of 3 fm, lattice spacing of 0.093 fm, and reproduces a pion mass of $260$ MeV. We use the quasi-distribution approach and employ three values of the proton momentum boost, 0.83 GeV, 1.25 GeV and 1.67 GeV. We use a source-sink separation of 1.12 fm to suppress excited-states contamination. The lattice data are renormalized non-perturbatively. We calculate the appropriate matching within Large Momentum Effective Theory, which is applied to the lattice data in order to obtain $g_T$. The final distribution is presented in the $\overline{\rm MS}$ scheme at a scale of 2 GeV. We also calculate the helicity distribution $g_1$ to test the Wandzura-Wilczek approximation for $g_T$. We find that the approximation works well for a large range in $x$. This work demonstrates the feasibility of accessing twist-3 parton distribution functions from novel methods within lattice QCD, and can provide important insights on the structure of hadrons.
晶格QCD对质子结构的启示:扭转-3部子分布函数gT(x)
在这项工作中,我们首次计算了晶格QCD中质子的扭转-3部子分布函数$g_T(x)$的等矢量风味组合。我们使用了两个简并光,一个奇异夸克和一个粲夸克($N_f=2+1+1$)的最大扭曲质量费米子的规范组态的集合,并进行了三叶草改进。晶格的空间范围为3fm,晶格间距为0.093 fm,再现了介子质量为260$ MeV。我们采用准分布方法,并采用三个质子动量推进值:0.83 GeV、1.25 GeV和1.67 GeV。我们使用1.12 fm的源汇分离来抑制激发态污染。晶格数据是非摄动的重整化。我们在大动量有效理论中计算了适当的匹配,并将其应用于晶格数据,以获得$g_T$。最终分布以$\overline{\rm MS}$方案给出,尺度为2 GeV。我们还计算了螺旋分布$g_1$来检验$g_T$的Wandzura-Wilczek近似。我们发现这个近似在x的大范围内很有效。这项工作证明了用新的方法在晶格QCD中获取扭转-3部子分布函数的可行性,并可以为强子的结构提供重要的见解。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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