Search for tau -> 3mu and test of light-lepton universality in tau decays at Belle II

• Kenta Uno (KEK)

Date: Jan 16, 2024 15:00 JST- Place: Kobaashi Hall and Zoom anguage: English Speaker: Kenta Uno (KEK) Title: Search for tau -> 3mu and test of light-lepton universality in tau decays at Belle II Zoom: topic: IPNS Seminar https://us02web.zoom.us/j/81258086591?pwd=WVRRdFY5MFlvRDlYM1BSZFluemZyZz09 meeting ID: 812 5808 6591 passcode: 952696 Abstract: Large number of tau leptons are produced at the SuperKEKB e+e- collider. The dataset collected by Belle II provides a unique opportunity to study the tau decays, especially on searches for lepton flavor violating decays of tau. Recentlly Belle II presented new results on the charged-lepton-flavor violating decay tau- -> mu- mu+ mu- and on a test of light-lepton universality between the decays tau- -> mu- nu nubar and tau- -> e- nu nubar, using the dataset collected in Run 1 (before summer 2022). For tau- -> mu- mu+ mu-, we obtained an upper limit of the branching fraction of 1.9 x 10^{-8}, which is the most stringent bounds despite the smaller data set compared to the previous results from Belle and BaBar.