Karlsruhe 2024 – scientific programme

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T: Fachverband Teilchenphysik

T 125: Flavour physics 6

T 125.2: Talk

Friday, March 8, 2024, 09:15–09:30, Geb. 30.41: HS 4

Branching fraction measurement of the rare decays B_(s)⁰ → π⁺ π⁻ µ⁺ µ⁻ at LHCb — Johannes Albrecht¹, Thomas Blake², •Jan Peter Herdieckerhoff¹, and Biljana Mitreska¹ — ¹TU Dortmund University, Dortmund, Germany — ²University of Warwick, Coventry, United Kingdom

Rare flavour-changing neutral current decays with b → q ℓ⁺ ℓ⁻ quark transitions (q=s,d) are sensitive probes of the Standard Model and thus among the measurements of interest to the LHCb experiment. Due to smaller CKM factors the b → d ℓ⁺ ℓ⁻ transition is even more suppressed than the b → s ℓ⁺ ℓ⁻ transition and therefore, less frequently detected at LHCb. With Run 1 data LHCb measured the decay B_s⁰ → π⁺ π⁻ µ⁺ µ⁻ with a significance of 7.2 σ. The decay B⁰ → π⁺ π⁻ µ⁺ µ⁻ was not yet observed, it was measured with a statistical significance of 4.8 σ. The main contributions to the studied channels are believed to proceed via the resonant decays B_s⁰ → f₀(980) (→ π⁺ π⁻) µ⁺ µ⁻ and B⁰ → ρ⁰(770) (→ π⁺ π⁻) µ⁺ µ⁻.

In this talk the current status of the branching fraction measurements of the B_(s)⁰ → π⁺ π⁻ µ⁺ µ⁻ decays using 8.9 fb⁻¹ of combined Run 1 and Run 2 data is presented. The possibility of performing a differential branching fraction measurement is explored.

Keywords: Rare Decays; LHCb; B physics; branching fraction; FCNC