在第四代存在下同时提取费米常数和PMNS矩阵元
Simultaneous Extraction of the Fermi constant and PMNS matrix elements in the presence of a fourth generation
摘要：
最近的几项研究进行的第四代夸克和轻子的约束遭受特设假设，即3 × 3幺正性持有的前三代中微子部门。只有在这个假设下，人们才能从μ子寿命测量中确定费米常数G_F，其精度为G_F = 1.16637（1）x 10^-5 GeV^-2。本文研究了如何在四代框架内从轻子和辐射μ和τ衰变以及带电π介子的K_13衰变和轻子衰变中提取G_F，并讨论了轻子普适性检验在这方面的作用。我们强调，第四代夸克和轻子味观测量和电弱精密观测量的约束只能得到一致的方式，如果这三个部门被认为是同时进行。在对轻子和辐射μ和τ衰变、K_13衰变以及带电π介子轻子衰变的联合拟合中，我们发现第四代矩阵元的p值为2.6%| U_{e 4}| =0的中微子混合矩阵。
英文摘要：
Several recent studies performed on constraints of a fourth generation of quarks and leptons suffer from the ad-hoc assumption that 3 x 3 unitarity holds for the first three generations in the neutrino sector. Only under this assumption one is able to determine the Fermi constant G_F from the muon lifetime measurement with the claimed precision of G_F = 1.16637 (1) x 10^-5 GeV^-2. We study how well G_F can be extracted within the framework of four generations from leptonic and radiative mu and tau decays, as well as from K_l3 decays and leptonic decays of charged pions, and we discuss the role of lepton universality tests in this context. We emphasize that constraints on a fourth generation from quark and lepton flavour observables and from electroweak precision observables can only be obtained in a consistent way if these three sectors are considered simultaneously. In the combined fit to leptonic and radiative mu and tau decays, K_l3 decays and leptonic decays of charged pions we find a p-value of 2.6% for the fourth generation matrix element |U_{e 4}|=0 of the neutrino mixing matrix.
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