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arXiv 2404.09856hep-phhep-ex
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匹配强子化与微扰演化：红外簇射截断依赖性视角下的簇模型

Matching Hadronization and Perturbative Evolution: The Cluster Model in Light of Infrared Shower Cutoff Dependence

André H. Hoang, Oliver L. Jin, Simon Plätzer, Daniel Samitz

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54 pages, 17 figures, published version
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AI总结：

本研究针对Herwig 7.2生成器，提出动态簇强子化模型，使部分子簇射截断$Q_0$作为红外因子化标度，实现$Q_0$不变性并与QCD因子化一致，改进$e^+e^-$双喷注度分布描述。

摘要：

在具有次领头对数（NLL）精度的部分子簇射的蒙特卡洛（MC）生成器背景下，终止簇射演化的截断值 $Q_0$ 应被视为红外因子化标度，从而使MC生成器的参数或非微扰效应具有场论解释，且具有可控的方案依赖性。这意味着生成器的部分子级应在QCD微扰论中以次领头阶精度仔细定义。此外，这还要求簇射截断 $Q_0$ 不被视为生成器的调谐参数之一，而是调谐可以在 $Q_0$ 值的一定范围内可靠进行，且强子级描述具有 $Q_0$ 不变性。这反过来对生成器的强子化模型行为施加了非平凡约束，使其参数在 $Q_0$ 值改变时能够相应调整。我们使用Herwig~7.2 MC生成器中实现的角有序部分子簇射和簇强子化模型研究这些特性，特别关注 $e^+e^-$ 双喷注度（2-jettiness）分布，其中簇射已知具有NLL精度，且QCD因子化对强子化修正施加严格约束。我们表明，Herwig默认的簇强子化模型不具备这些特性，也未以令人满意的精度与QCD因子化保持一致。我们设计了对簇强子化模型的修改，添加了默认模型中缺失的一些动态部分子簇射方面。对于这种新颖的动态簇强子化模型，这些特性以及与QCD因子化的一致性得以更精确地实现。

英文摘要：

In the context of Monte Carlo (MC) generators with parton showers that have next-to-leading-logarithmic (NLL) precision, the cutoff $Q_0$ terminating the shower evolution should be viewed as an infrared factorization scale so that parameters or non-perturbative effects of the MC generator may have a field theoretic interpretation with a controllable scheme dependence. This implies that the generator's parton level should be carefully defined within QCD perturbation theory with subleading order precision. Furthermore, it entails that the shower cut $Q_0$ is not treated as one of the generator's tuning parameters, but that the tuning can be carried out reliably for a range of $Q_0$ values and that the hadron level description is $Q_0$-invariant. This in turn imposes non-trival constraints on the behavior of the generator's hadronization model, so that its parameters can adapt accordingly when the $Q_0$ value is changed. We investigate these features using the angular ordered parton shower and the cluster hadronization model implemented in the Herwig~7.2 MC generator focusing in particular on the $e^+e^-$ 2-jettiness distribution, where the shower is known to be NLL precise and where QCD factorization imposes stringent constraints on the hadronization corrections. We show that the Herwig default cluster hadronization model does not exhibit these features or consistency with QCD factorization with a satisfying precision. We design a modification of the cluster hadronization model, where some dynamical parton shower aspects are added that are missing in the default model. For this novel dynamical cluster hadronization model these features and consistency with QCD factorization are realized much more accurately.

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