Test of lepton-flavor universality in decays at Belle

Wehle, S.*; 谷田 聖; Belle Collaboration*; 他179名*

Physical Review Letters, 126(16), p.161801_1 - 161801_8, 2021/04

https://doi.org/10.1103/PhysRevLett.126.161801

We present a measurement of , the branching fraction ratio / , for both charged and neutral mesons. The ratio for the charged case, , is the first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass, . The analysis is based on a data sample of , containing events, recorded at the resonance with the Belle detector at the KEKB asymmetric-energy collider. The obtained results are consistent with Standard Model expectations.