Erlangen 2026 – scientific programme

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T: Fachverband Teilchenphysik

T 72: Flavour Physics IV

T 72.1: Talk

Thursday, March 19, 2026, 16:15–16:30, KH 01.011

Early Studies on rare B_s⁰→ µ⁺µ⁻ decays and related control modes in Run 3 at the LHCb experiment — Johannes Albrecht, •Lukas Bertsch, Mick Mulder, Katharina Popp, and Jan Wagner — TU Dortmund University, Germany

Rare B_(s)⁰→ µ⁺µ⁻ decays provide a sensitive test of the Standard Model owing to their exceptional suppression, clean experimental signature, and precise theoretical predictions. Searches for these decays have been conducted since the start of the LHCb experiment, accomplishing the observation of B_s⁰→ µ⁺µ⁻ in 2014, together with the CMS collaboration. However, the more strongly suppressed B⁰ meson counterpart of the decay has not yet been measured with statistical significance, due to interfering backgrounds and limited data. Much larger datasets collected during Run 3 of the LHC provide a clear opportunity to find evidence for the B⁰→ µ⁺µ⁻ decay, but also pose new challenges due to the busy collision environment. Therefore, early studies on the new dataset are performed in this work, providing a first implementation of required analysis tools and verifying the analysis procedure on Run 3 data. Based on 11 fb⁻¹ of data recorded in 2024 and early 2025, branching fractions of control modes are measured following the signal-channel analysis strategy, and a preliminary estimate of the sensitivity to the B⁰→ µ⁺µ⁻ decay is obtained.

Keywords: Rare decays; FCNC; B physics; B2mumu; Run 3