Erlangen 2026 – scientific programme
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T: Fachverband Teilchenphysik
T 8: Flavour Physics I
T 8.5: Talk
Monday, March 16, 2026, 17:15–17:30, KH 01.011
Measurement of the Differential Branching Ratio, Lepton Angular Distribution and Determination of the CKM Matrix Element |Vcb| in Inclusive B → Xc ℓ ν Semileptonic Decays using Belle II Data — •Rajeshwari Roy, Florian Bernlochner, Markus Prim, and Munira Khan — Physikalische Institut der Rheinische Friedrich-Wilhelms- Universität Bonn
We present a measurement of the differential branching ratio and lepton angular distribution in inclusive semileptonic B → Xc ℓ ν decays using data collected with the Belle II detector corresponding to an integrated luminosity of 365 fb−1, recorded at the Υ(4S) resonance. Signal candidates (b → c ℓ νℓ) are selected using a tag-side full-event interpretation, enabling precise reconstruction of the kinematics in the inclusive decay. The differential branching ratios as functions of the lepton momentum, momentum transfer q2, and lepton helicity angle cosθℓ are calculated incorporating efficiency corrections and including a comprehensive evaluation of systematic uncertainties using the Sysvar framework, which provides a consistent treatment of arbitrary correlations arising from systematic effects affecting shapes in simultaneous template fits. A global fit to the measured spectra within the HQE formalism yields an updated determination of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb|, contributing to resolving the difference between inclusive and exclusive determinations of |Vcb|.
Keywords: Semileptonic B decays; CKM matrix element