具有高阶扭转和靶质量修正的极化部分子分布函数的NNLO确定
NNLO Determination of Polarized Parton Distribution Functions with Higher-Twist and Target-Mass Corrections
AI总结：
该研究基于包容性极化深度非弹性散射数据集，用NNLO QCD分析极化部分子分布函数，得到\texttt{KLS26}集。考虑加性和乘性HT参数化估计不确定性，评估NNLO修正影响，还进行额外拟合，其结果为核子自旋结构精确研究提供更新确定。
AI中文摘要：
我们基于包容性极化深度非弹性散射（DIS）的世界数据集，对极化部分子分布函数（PDFs）进行了次下一个领头阶（NNLO）的量子色动力学（QCD）分析。得到的PDF集表示为\texttt{KLS26}，在完全的NNLO框架内，对靶质量修正（TMCs）、高阶扭转（HT）贡献和正性约束进行了一致处理。为估计与非微扰功率修正相关的残余理论不确定性，考虑了加性和乘性HT参数化。尽管这两种方法导致不同的高阶扭转系数，但当前结果在不确定性范围内产生了非常相似的拟合质量和兼容的极化PDFs。通过与NLO下的KLSS21极化PDF确定进行比较，评估了NNLO修正的影响，显示出极化奇异夸克分布中最明显的变化，胶子扇区有适度修改，上夸克和下夸克螺旋度分布的影响较小。将非单态轴向电荷作为自由参数的额外拟合，以及不同的高阶扭转实现，在PDFs中引起了小但依赖味的修改，在极化奇异夸克分布中影响最明显，对胶子有适度敏感性。\texttt{KLS26}集建立了对螺旋度相关部分子分布的更新确定，为未来核子自旋结构的精确研究提供了可能。
英文摘要：
We present a next-to-next-to-leading order (NNLO) QCD analysis of polarized parton distribution functions (PDFs) based on the world data set of inclusive polarized deep-inelastic scattering (DIS). The resulting PDF set, denoted as \texttt{KLS26}, includes a consistent treatment of target-mass corrections (TMCs), higher-twist (HT) contributions, and positivity constraints within a fully NNLO framework. To estimate the residual theoretical uncertainty associated with nonperturbative power corrections, both additive and multiplicative HT parametrizations are considered. Although these two approaches lead to different higher-twist coefficients, the current results yield very similar fit qualities and compatible polarized PDFs within uncertainties. The impact of NNLO corrections is assessed through a comparison with the KLSS21 polarized PDF determination at NLO, showing the most visible changes in the polarized strange-quark distribution, together with moderate modifications in the gluon sector and smaller effects in the up- and down-quark helicity distributions. Additional fits treating the nonsinglet axial charges as free parameters, together with different higher-twist implementations, induce small but flavor-dependent modifications in the PDFs, with the most noticeable effects in the polarized strange-quark distribution and moderate sensitivity in the gluon. The \texttt{KLS26} set establishes an updated determination of helicity-dependent parton distributions, enabling future precision studies of nucleon spin structure.
