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Test of lepton universality with W boson decays

用 W 玻色子衰变检验轻子普遍性

基本信息

批准号：
2108737
负责人：
金额：
--
依托单位：
University of Warwick
依托单位国家：
英国
项目类别：
Studentship
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=studentship-2108737
关键词：
Test lepton universality boson decays

项目摘要

This project aims to exploit the large LHCb Run-II dataset to make a precision test of lepton universality with W boson decays.In the standard model the W boson decays with equal branching fraction, up to tiny corrections, to the three generations of leptons.For more than a decade there has been an anomalous measurement, by experiments at the LEP collider, of the W branching ratio to third generation leptons.This is yet to be tested by any other experiment. Furthermore there have been several recent measurements by three different experiments, including LHCb, which hint at a violation of lepton universality in beauty hadron decays.LHCb is well suited to make the first test of the LEP anomaly, using muonic decays of the tau lepton.This is thanks to its ability to trigger on soft muons, and to resolve the subtle impact parameter signature of the tau decay.The idea will be to measure the ratio of the decay rate of W->mu nu compared to that of W -> tau nu, with the single muon final state.Developing a strategy to subtract the background from high transverse momentum charm hadron decays will be one of the main challenges.Novel statistical methods will be required in order to exploit different control samples and observables to constrain the effect of this background.This promises to be a very excited research project, which addresses a timely and important physics question, and has the potential for a high impact result.

本项目旨在利用LHCb Run-II大型数据集对W玻色子衰变的轻子普适性进行精确的检验。在标准模型中，W玻色子以相等的分支分数衰变，直到微小的修正，三代轻子。十多年来，在LEP对撞机上的实验中，第三代轻子的W分支比。这还有待于任何其他实验的检验。此外，最近有三个不同的实验进行了几次测量，包括LHCb，这暗示了美强子衰变中轻子普适性的违反。LHCb非常适合使用τ轻子的μ子衰变进行LEP异常的第一次测试。这要归功于它能够触发软μ子，并解析τ衰变的微妙影响参数特征。这个想法将是测量W-> μ nu的衰变率与W -> τ nu的衰变率之比，用单μ子末态。发展一种从高横动量粲强子衰变中减去背景的策略将是主要挑战之一。需要新的统计方法来利用不同的控制样本和可观测量来限制这种背景的影响。这将是一个非常令人兴奋的研究项目，它解决了一个及时和重要的物理问题，并有可能产生高影响力的结果。