Search for Lepton-Flavor-Violating τ Decays to a Lepton and an Invisible Boson at Belle II

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Date
2023-05-02, 2023-05-02
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Publisher
AMER PHYSICAL SOC
Abstract

We search for lepton-flavor-violating τ-→e-α and τ-→μ-α decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8 fb-1, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ-→e-ν¯eντ and τ-→μ-ν¯μντ decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ-→e-α)/B(τ-→e-ν¯eντ) in the range (1.1-9.7)×10-3 and on B(τ-→μ-α)/B(τ-→μ-ν¯μντ) in the range (0.7-12.2)×10-3 for α masses between 0 and 1.6 GeV/c2. These results provide the most stringent bounds on invisible boson production from τ decays.

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Keywords
Science & Technology, Physical Sciences, Physics, Multidisciplinary, Physics, LOWEST-ORDER CALCULATIONS, RADIATIVE-CORRECTIONS, MONTE-CARLO, FINAL-STATES, SIMULATION, Belle II Collaboration, 5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences, 40 Engineering, 49 Mathematical sciences
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