Measurement of B⁺→τ⁺ν_τ branching fraction with a hadronic tagging method at Belle II

2025/02/07 by Belle II Collaboration, Adachi, I., Adamczyk, K. +341
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex)

paper · doi:10.48550/arxiv.2502.04885

Abstract

We present a measurement of the branching fraction of B⁺→τ⁺ν_τ decays using (387±6)× 10⁶ Υ(4S) collected between 2019 and 2022 with the Belle II detector at the SuperKEKB e⁺e^- collider. We reconstruct the accompanying B^- meson using the hadronic tagging method, while B⁺→τ⁺ν_τ candidates are identified in the recoil. We find evidence for B⁺→τ⁺ν_τ decays at 3.0 standard deviations, including systematic uncertainties. The measured branching fraction is B(B⁺→τ⁺ν_τ) = [1.24 ± 0.41 (stat.) ± 0.19 (syst.)] × 10^-4.

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