In this seminar I will present the first simultaneous test of muon-electron universality in ๐ต+โ๐พ+โ+โโ and ๐ต0โ๐พโ0โ+โโ decays, known as ๐
(๐พ) and ๐
(๐พโ), in two regions of di-lepton invariant mass squared.
The analysis operates at a higher signal purity compared with previous analyses and implements a data-driven treatment of residual hadronic backgrounds. The analysis uses the full LHCb Run 1 and 2 data recorded in 2011-2012 and 2015-2018, corresponding to an integrated luminosity of 9 fbโ1. This analysis is the most sensitive lepton universality test in rare b-decays and the results obtained supersede the previous LHCb measurements of ๐
(๐พ) and ๐
(๐พโ0).