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T: Fachverband Teilchenphysik

T 129: Flavor X

T 129.5: Talk

Thursday, March 23, 2023, 18:30–18:45, HSZ/0304

Probing lepton universality in inclusive semileptonic B-meson decays at Belle II — Florian Bernlochner, Jochen Dingfelder, •Henrik Junkerkalefeld, and Peter Lewis for the Belle II collaboration — Physikalisches Institut der Rheinischen Friedrich-Wilhelms-Universität Bonn

Excesses in the ratios R(D^(*)) = B (B → D^(*)τν) / B (B → D^(*)ℓν) measured by BaBar, Belle and LHCb have created large interest in recent years. Together with other measurements in the flavor sector they may hint at non-universality of lepton couplings. The Belle II experiment in Japan enables a complementary test of these measurements. Due to the precise knowledge of the initial state of the collision and the controlled production of BB pairs, an inclusive measurement of R(X_τ/ℓ) = B (B → Xτν) / B (B → Xℓν) as well as the light-lepton ratio R(X_e/µ) = B (B → X eν) / B (B → Xµν) becomes possible. Here, the hadronic system X is not constrained to specific final states, i.e., all possible B-meson decay modes contribute. In this talk, the results of the R(X_e/µ) measurement based on a Belle II dataset of 189 fb⁻¹ are presented and the current status of the R(X_τ/ℓ) measurement is discussed.