Bonn 2020 – scientific programme

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T: Fachverband Teilchenphysik

T 9: Flavor physics: Lepton universality tests I

T 9.4: Talk

Monday, March 30, 2020, 17:15–17:30, H-HS X

Signal extraction of B⁰ → π⁻ τ⁺ ν_τ at Belle and Belle II — Jochen Dingfelder, Peter Lewis, and •Lu Xu for the Belle II collaboration — Physikalisches Institut, Universität Bonn, Bonn, Germany

The decay B⁰ → π⁻ τ⁺ ν_τ is sensitive to new physics beyond the Standard Model, such as contributions from charged Higgs bosons or leptoquarks. The world’s best limit was established by the Belle experiment using its full dataset, measuring B(B⁰ → π⁻ τ⁺ ν_τ) < 2.5 × 10⁻⁴ at 90% confidence level. We present the current status of an ongoing measurement of B(B⁰ → π⁻ τ⁺ ν_τ) with improved hadronic tagging in leptonic and hadronic τ decay modes. The study aims to extract the ratio R(π) = B(B⁰ → π⁻ τ⁺ ν_τ) / B(B⁰ → π⁻ ℓ⁺ ν_ℓ) with ℓ denoting either an electron or muon. A MVA based on a boosted decision tree is employed to separate light lepton and τ contributions from each other.