迈向N$^3$LO CT全局PDF分析：DIS中的SACOT-$\chi$方案与部分N$^3$LO的DGLAP演化
Toward N$^3$LO CT global PDF analyses: The SACOT-$χ$ scheme in DIS and DGLAP evolution at partial N$^3$LO
AI总结：
CTEQ-TEA团队提出SACOT-$\chi$方案在DIS中实现pN$^3$LO计算，扩展Candia算法至N$^3$LO DGLAP演化，并给出初步CT25拟合，推动全局PDF分析超越NNLO精度。
AI中文摘要：
我们讨论了CTEQ-TEA团队在QCD中超越NNLO精度的全局部分子分布函数（PDF）分析方面正在进行的工作的三个层面。首先，我们提出了SACOT-$\chi$通用质量变味数方案在QCD部分次次次领头阶（pN$^3$LO）下用于深非弹性散射（DIS）的一种实现。我们数值上说明了该SACOT-$\chi$理论预测如何通过包含可用的$O(\alpha_s^3)$贡献来捕捉DIS结构函数对重夸克质量的依赖。其次，我们讨论了一个初步的pN$^3$LO CT25拟合，该拟合实现了此类贡献。第三，我们将用于在$x$空间中求解非极化部分子分布函数（PDF）的DGLAP演化方程的Candia算法扩展到QCD的N$^3$LO。该算法基于解的对数展开，并可扩展到QCD中的所有阶。在非单态扇区中，我们给出了与N$^3$LO下精确DGLAP解等价的展开。我们展示了使用QCD中4环分裂函数的最新近似演化的近似N$^3$LO PDF的结果。
英文摘要：
We discuss three aspects of the ongoing efforts of the CTEQ--TEA group toward global parton distribution function (PDF) analyses beyond NNLO accuracy in QCD. First, we present a realization of the SACOT-$χ$ general-mass variable flavor number scheme for deep-inelastic scattering (DIS) at the partial next-to-next-to-next-to-leading order (pN$^3$LO) in QCD. We numerically illustrate how this SACOT-$χ$ theory prediction captures the dependence of DIS structure functions on masses of heavy quarks with inclusion of the available $O(α_s^3)$ contributions. Second, we discuss a preliminary pN$^3$LO CT25 fit that implements such contributions. Third, we extend the Candia algorithm for solving DGLAP evolution equations for unpolarized parton distribution functions (PDFs) in $x$ space to N$^3$LO in QCD. The algorithm is based on logarithmic expansions of the solution and can be extended to all orders in QCD. An expansion equivalent to the exact DGLAP solution at N$^3$LO is presented in the non-singlet sector. We show results for approximate N$^3$LO PDFs evolved using the most recent approximations to the 4-loop splitting functions in QCD.
