Karlsruhe 2024 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 102: Flavour physics 4

T 102.1: Vortrag

Donnerstag, 7. März 2024, 16:00–16:15, Geb. 30.41: HS 4

Isospin asymmetry in B → K µ⁺ µ⁻ decays — Johannes Albrecht¹, •Fabio De Vellis¹, Cristoph Langenbruch², Vitalii Lisovskyi³, Biljana Mitreska¹, Thomas Oeser⁴, and Stefan Schael⁴ — ¹TU Dortmund University, Dortmund, Germany — ²Heidelberg University, Heidelberg, Germany — ³EPFL, Lausanne, Switzerland — ⁴RWTH Aachen University, Aachen, Germany

Symmetries in the Standard Model come from very fundamental aspects of the theory, and tests of them play a determinant role in the understanding of the whole picture of elementary particles. Isospin symmetry predicts a branching fraction that is almost the same for decays which differ only by one spectator quark, like B⁰ → K⁰ µ⁺ µ⁻ and B⁺ → K⁺ µ⁺ µ⁻. For these decays, a quantity which describes differences in branching fraction, namely the asymmetry, can be defined. This is particularly convenient since it is theoretically clean and it allows canceling some experimental uncertainties.

Previous measurements on these decays from LHCb and Belle, despite being compatible with Standard Model expectations, suggested coherent deviations that could be interpreted as statistical fluctuations, or unaccounted theoretical uncertainties, or as a sign of New Physics.

In this talk an update of the asymmetry measurement on data collected at LHCb and corresponding to an integrated luminosity of 9 fb⁻¹ is presented.

Keywords: LHCb; Rare decays; Isospin asymmetry; Electroweak penguin