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T: Fachverband Teilchenphysik
T 9: Flavour Physics I
T 9.1: Vortrag
Montag, 31. März 2025, 16:45–17:00, VG 1.104
Search for B+ → K*+ τ ℓ with hadronic tagging at the Belle II experiment — •Lara Fuchs, Torben Ferber, Pablo Goldenzweig, and Raynette van Tonder — Institute of Experimental Particle, Karlsruhe Institute of Technology, Karlsruhe, Germany
Current measurements of semileptonic B meson decays are in tension with Standard Model predictions, giving rise to a plethora of proposed New Physics models to explain the observed results. These models not only incorporate lepton flavor violation, but also predict significantly enhanced rates for lepton flavor violating decays involving second- and third-generation leptons. Among these processes, flavor-changing neutral current transitions such as b → s τ ℓ are further suppressed, and thus especially sensitive to New Physics contributions.
In this talk, we present the status of the first search for B+ → K*+ τ ℓ, conducted at the Belle II experiment, located at the SuperKEKB asymmetric e+e− collider. We employ a hadronic tagging approach where the accompanying B meson in e+e−→Υ(4S)→ B+B− events is fully reconstructed via hadronic decay chains. The complete knowledge of the tag-side particle’s four-momentum combined with the well-known event energy allow for a direct determination of the invariant mass of the system recoiling against the Btag K*+ℓ system. This provides a reliable method for signal extraction despite the presence of missing energy in the decay, making Belle II an excellent experiment for conducting this search.
Keywords: Belle II Experiment; B Physics; Lepton Flavor Violation; Rare B Decays; Flavor-changing Neutral Currents