Crivellin Andreas, Hoferichter Martin, Manzari Claudio Andrea
Theory Division, CERN, CH-1211 Geneva 23, Switzerland.
Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Phys Rev Lett. 2021 Aug 13;127(7):071801. doi: 10.1103/PhysRevLett.127.071801.
The Fermi constant G_{F} is extremely well measured through the muon lifetime, defining one of the key fundamental parameters in the standard model (SM). Therefore, to search for physics beyond the SM (BSM) via G_{F}, the constraining power is determined by the precision of the second-best independent determination of G_{F}. The best alternative extractions of G_{F} proceed either via the global electroweak (EW) fit or from superallowed β decays in combination with the Cabibbo angle measured in kaon, τ, or D decays. Both variants display some tension with G_{F} from muon decay, albeit in opposite directions, reflecting the known tensions within the EW fit and hints for the apparent violation of Cabibbo-Kobayashi-Maskawa unitarity, respectively. We investigate how BSM physics could bring the three determinations of G_{F} into agreement using SM effective field theory and comment on future perspectives.
费米常数(G_{F})通过μ子寿命得到了极其精确的测量，它是标准模型（SM）中的关键基本参数之一。因此，要通过(G_{F})寻找标准模型之外的物理（BSM），其约束能力取决于(G_{F})的次优独立测定的精度。(G_{F})的最佳替代提取方法要么通过全局电弱（EW）拟合，要么通过超允许β衰变结合在K介子、τ子或D介子衰变中测量的卡比博角来进行。这两种方法都与来自μ子衰变的(G_{F})存在一些张力，尽管方向相反，分别反映了EW拟合中已知的张力以及明显违反卡比博 - 小林 - 益川幺正性的迹象。我们使用标准模型有效场论研究BSM物理如何能使(G_{F})的三种测定结果达成一致，并对未来前景进行评论。
