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.

该项目旨在利用大型 LHCb Run-II 数据集对 W 玻色子衰变的轻子普遍性进行精确测试。在标准模型中，W 玻色子以相等的分支分数衰变，直至微小修正，直至三代轻子。十多年来，通过 LEP 对撞机的实验，对第三代轻子的 W 分支比进行了异常测量。这尚未通过任何其他实验进行测试。此外，包括 LHCb 在内的三个不同实验最近进行了一些测量，这暗示了美丽强子衰变中轻子普遍性的违反。LHCb 非常适合使用 tau 轻子的 μ 子衰变来对 LEP 异常进行首次测试。这要归功于它能够触发软 μ 子，并解决 tau 衰变的微妙影响参数特征。这个想法是测量 W->mu nu 的衰变率与W -> tau nu，具有单μ子最终状态。开发一种从高横向动量魅力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。这有望成为一个非常令人兴奋的研究项目，它解决了一个及时而重要的物理问题，并有可能产生高影响力的结果。