# New tests of lepton universality using rare B decays with $K_{S}^{0}$ mesons in the final state at LHCb

- Institution: CERN
- Department: LHC Seminar
- Speaker: Harry Victor Cliff
- Year: 2021
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3013668)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

In recent years several intriguing anomalies have been reported in the rare decays of B mesons. Most prominently, in March 2021 a measurement by LHCb of the ratio known as $R_K$ showed 3.1 standard deviation significance for the violation of lepton universality in $B^{+} \rightarrow K^{+} \ell^{+} \ell^{-}$ decays, where $\ell$ is either a muon or an electron. Previous measurements of the ratio $R_{K*}$ using $B^{0}\rightarrow K^{*0} \ell^{+} \ell^{-}$ also hinted at the violation of lepton universality, albeit at a lower statistical significance.

In this seminar we present the first tests at LHCb of lepton universality using these decays' isospin partners - $B^{0} \rightarrow K^{0}_{S} \ell^{+} \ell^{-}$ and $B^{+} \rightarrow K^{*+} \ell^{+} \ell^{-}$ .

These tests have lower statistical sensitivity than $R_K$ and $R_{K*}$ due to the presence of a $K^0_{\text{S}}$ in the final state. The measurements are performed with data recorded by the LHCb experiment in 2011-2012 and 2016-2018, corresponding to an integrated luminosity of 9 $\text{fb}^{-1}$.

The seminar will take place in "hybrid format" with the speaker present in-person in the Auditorium. Note that the occupancy is currently limited to 70 people due to hygiene rules. If you want to attend in person you must register.

LHCb seminar 19 October 2021: https://cern.zoom.us/j/63783938547?pwd=QUdqRzdGNDI5M0xwc1NVNXVrRWpaZz09.

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## Lectures

1. [New tests of lepton universality using rare B decays with $K_{S}^{0}$ mesons in the final state at LHCb](https://invisiblenetwork.ai/learn/cern/3013668/a82825481b85), 1 h 2 min (CERN's player)