Cyrille Praz

15 May 2023

Abstract: Decays of B mesons involving the transition of a b quark into an s quark are good probes of physics beyond the standard model. Such decays are studied at the Belle II experiment, a detector located along the SuperKEKB electron-positron collider, and with data corresponding to an integrated luminosity of 189 fb−1 collected at the energy of the Υ(4S) resonance. The radiative decay of a B meson into inclusive final states involving a strange hadron and a photon (B → Xs γ) is studied by fully reconstructing the partner B meson in a hadronic decay. The photon-energy spectrum and the branching fraction of the inclusive B → Xsγ decay are reported. In addition, the branching fraction of the decay of a B meson into an excited K meson and a pair of charged leptons (B → K∗(892)l+l− , with l+l− either an electron-positron or a muon-antimuon pair) is reported. A control channel for the study of the charmless B → Kl+l− decay is the decay B → J/ψ(l+l− )K, for which a lepton-flavour universality ratio is reported. All the reported measurements are in agreement with the world averages and the standard model predictions.

Keyword(s): EWP ; Electroweak ; Penguin ; Radiative ; Moriond ; 2023
Note: Proceedings of "Rencontres de Moriond EW 2023"