We explore the role of parametrizations for nonperturbative QCD functions in global analyses, with a specific application to extending a phenomenological analysis of the parton distribution functions (PDFs) in the charged pion realized in the xFitter fitting framework. The parametrization dependence of PDFs in our pion fits substantially enlarges the uncertainties from the experimental sources estimated in the previous analyses. We systematically explore the parametrization dependence by employing a novel technique to automate generation of polynomial parametrizations for PDFs that makes use of Bézier curves. This technique is implemented in a c++ module fantômas that is included in the xFitter program. Our analysis reveals that the sea and gluon distributions in the pion are not well disentangled, even when considering measurements in leading-neutron deep inelastic scattering. For example, the pion PDF solutions with a vanishing gluon and large quark sea are still experimentally allowed, which elevates the importance of ongoing lattice and nonperturbative QCD calculations, together with the planned pion scattering experiments, for conclusive studies of the pion structure.

中文翻译：

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使用贝塞尔参数化分析 pion 中的部分子分布

我们探讨了非微扰 QCD 函数参数化在全局分析中的作用，具体应用是扩展 xFitter 拟合框架中实现的带电 pion 中的部分子分布函数 (PDF) 的唯象分析。我们的 pion 拟合中 PDF 的参数化依赖性大大扩大了先前分析中估计的实验来源的不确定性。我们通过采用一种新技术来自动生成利用贝塞尔曲线的 PDF 多项式参数化，系统地探索了参数化依赖性。该技术在 xFitter 程序中包含的C ++ 模块fantômas中实现。我们的分析表明，即使考虑前导中子深非弹性散射的测量，π介子中的海和胶子分布也没有很好地解开。例如，具有消失胶子和大夸克海的π介子PDF解在实验上仍然是允许的，这提高了正在进行的晶格和非微扰QCD计算以及计划的π介子散射实验对于介子结构的结论性研究的重要性。