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arXiv 2202.00969hep-ph
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实现精确的对撞机预测:Parton分支方法

Towards precise collider predictions: the Parton Branching method

Aleksandra Lelek

摘要:

共线因式分解定理,结合微扰QCD中的有限阶计算,提供了一个强有力的框架,以获得许多对撞机可观测量的预测。然而,对于涉及多个能量标度的可观测量,横向自由度不能被忽略,有限阶微扰计算必须与QCD运行耦合中所有阶的计算相结合,以获得可靠的理论预测,能够描述实验测量。传统上,这是通过解析再确认方法或部分子簇射(PS)蒙特卡罗(MC)方法来完成的。在这次演讲中,我们提出了部分子分支(PB)MC方法,以获得基于横向动量相关(TMD)因子分解的QCD对撞机预测。PB提供了TMD部分子分布函数(PDF)的演化方程,在将TMD PDF与实验数据拟合后,可用于TMD MC事件发生器。我们提出的方法的基本概念,并说明其应用程序的对撞机测量集中在Drell-Yan(DY)轻子对生产在不同的运动范围内,从固定目标的LHC能量。我们讨论了该方法的最新发展,特别是集中在匹配的次领先阶(NLO)的TMD演化与MC在NLO计算的NLO矩阵元素。

英文摘要:

The collinear factorization theorem, combined with finite-order calculations in perturbative QCD, provides a powerful framework to obtain predictions for many collider observables. However, for observables which involve multiple energy scales, transverse degrees of freedom cannot be neglected, and finite-order perturbative calculations have to be combined with resummed calculations to all orders in the QCD running coupling in order to obtain reliable theoretical predictions, capable of describing experimental measurements. This is traditionally done either by analytic resummation methods or by parton shower (PS) Monte Carlo (MC) methods. In this talk we present the Parton Branching (PB) MC method to obtain QCD collider predictions based on Transverse Momentum Dependent (TMD) factorization. The PB provides evolution equations for TMD Parton Distribution Functions (PDFs) which, upon fitting TMD PDFs to experimental data, can be used in TMD MC event generators. We present the basic concepts of the method and illustrate its applications to collider measurements focusing on Drell-Yan (DY) lepton-pair production in different kinematic ranges, from fixed-target to LHC energies. We discuss the latest developments of the method concentrating especially on the matching of next-to-leading-order (NLO) TMD evolution with MC-at-NLO calculations of NLO matrix elements.

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