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T: Fachverband Teilchenphysik

T 81: Flavour physics IV

T 81.6: Vortrag

Donnerstag, 18. März 2021, 17:15–17:30, Tf

Measurement of the ratio R_{K^{∗ 0}} using Run 1 + 2 data of the LHCb experiment — •Stephan Escher, Christoph Langenbruch, Stefan Schael, Sebastian Schmitt, and Eluned Smith — RWTH Aachen (Germany)

In the Standard Model (SM) of particle physics flavour-changing neutral-current processes are forbidden at tree-level and can only occur in electroweak loop diagrams. Therefore, b→ s transitions are rare and sensitive to heavy particles beyond the SM. In the SM the coupling of gauge bosons to leptons are independent of their flavour, which is known as lepton flavour universality (LFU). Thus, the R_{K^{∗ 0}} ratio, defined as R_{K^{∗ 0}}=B(B⁰→ K^{∗ 0}µ⁺µ⁻)/B(B⁰→ K^{∗ 0}e⁺e⁻), is predicted to be unity in the SM (neglecting lepton mass effects). The existence of new particles, that couple differently to electrons and muons, could influence the R_{K^{∗ 0}} ratio significantly and lead to deviations from unity.

To this date, the most precise measurement of R_{K^{∗ 0}} is performed by the LHCb collaboration using Run 1 data showing a deviation of 2.4−2.5 standard deviations (σ) from the SM expectations.

This talk will present the updated R_{K^{∗ 0}} analysis using the combined Run 1 and 2 LHCb data sample, which is currently in LHCb review. Particular emphasis will be on the validation of fit yields and efficiencies of the control channel as well as on rare mode fits and sensitivities.