arXiv 1209.47332012-09-21hep-ph

LHC中Drell-Yan过程轻子横动量的电荷不对称性

Charge asymmetries of lepton transverse momenta in Drell-Yan processes at the LHC

M. W. Krasny, W. Placzek

备注：: 18 pages, 8 figures

摘要：

在大型强子对撞机上，在精确测量标准模型参数（如W玻色子的质量和宽度、它们的电荷不对称性和sin ^2（θ_W））时，德雷尔-杨过程中的带电轻子横动量起着重要作用。因此，蒙特卡罗事件发生器应尽可能准确地描述它们的分布。在本文中，我们讨论的问题，匹配的硬过程运动学的Monte Carlo发生器WINHAC与部分子簇射运动学的PYTHIA 6.4发生器，同时接口这两个程序。我们表明，在LO矩阵元计算中，夸克和反夸克有效动量的不适当分配可能会对轻子横动量的预测产生很大影响，甚至完全逆转它们在LHC上的电荷不对称性。我们提出了两种匹配方案，其中轻子运动学变量的NLO QCD分布可以很好地由LO WINHAC发生器再现。

英文摘要：

Charged lepton transverse momenta in the Drell-Yan processes play an important role at the LHC in precision measurements of the Standard Model parameters, such as the W-boson mass and width, their charge asymmetries and sin^2(theta_W). Therefore, their distributions should be described as accurate as possible by the Monte Carlo event generators. In this paper we discuss the problem of matching the hard-process kinematics of the Monte Carlo generator WINHAC with the parton-shower kinematics of the PYTHIA 6.4 generator while interfacing these two programs. We show that improper assignment of the quark and antiquark effective momenta in the LO matrix element computations may affect considerably the predicted lepton transverse momenta and even completely reverse their charge asymmetries at the LHC. We propose two matching schemes in which the NLO QCD distributions of the leptonic kinematical variables can be well reproduced by the LO WINHAC generator.

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英文摘要：

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