Heidelberg 2022 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 3: Flavour Physics 1

T 3.5: Vortrag

Montag, 21. März 2022, 17:15–17:30, T-H16

Measurement of R(D*) with semileptonic tagging at Belle II — Florian Bernlochner, Jochen Dingfelder, Peter Lewis, and •Alina Manthei for the Belle II collaboration — Physikalisches Institut der Rheinischen Friedrich-Wilhelms-Universität Bonn

The Belle II experiment at the SuperKEKB asymmetric-energy electron-positron collider is able to collect a large number of events with BB pairs. The analysis of semitauonic decays of these B mesons allows for tests of lepton flavour universality. Existing experimental results on the ratios of the branching fractions R(D^(*) =B(B→ D^(*) τ⁻ ν) / B( B → D^(*) l⁻ν), where l denotes an electron or muon, are in tension with the Standard Model (SM) predictions, which might hint at physics beyond the SM, such as the presence of charged Higgs bosons or leptoquarks. A combined analysis of R(D) and R(D^*) with measurements from Belle, BaBar and LHCb yields a divergence from the SM prediction by approximately 3.8σ, where σ indicates the standard deviation. Thus, further investigations of these decays with the recently collected data by Belle II are necessary. This talk will present the current status and plans for a measurement of R(D^(*)) using this data, while reconstructing the respective other B meson in the event in semileptonic modes.