Dortmund 2021 – wissenschaftliches Programm
T 81.6: Vortrag
Donnerstag, 18. März 2021, 17:15–17:30, Tf
Measurement of the ratio RK∗ 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 RK∗ 0 ratio, defined as RK∗ 0=B(B0→ K∗ 0µ+µ−)/B(B0→ K∗ 0e+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 RK∗ 0 ratio significantly and lead to deviations from unity.
To this date, the most precise measurement of RK∗ 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 RK∗ 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.