Experimental results tending to show lepton universality violations (i.e. a different probability for decays to tau leptons, muons, and electron-positron pairs respectively, mass-energy conservation permitting) are the most notable experimental anomalies from Standard Model predictions outstanding right now in high energy physics.
But the statistical significance is merely a tension that may fade with a major new data point like the one to be announced on Tuesday, and there isn't a good explanation for why it isn't seen in other phenomena that should involve the same intermediate W boson decay driven processes.
Measurements of 𝑅(𝐾) and 𝑅(𝐾∗) with the full LHCb Run 1 and 2 databy Renato Quagliani (EPFL - Ecole Polytechnique Federale Lausanne (CH))In this seminar we present the first simultaneous test of muon-electron universality in 𝐵+→𝐾+ℓ+ℓ− and 𝐵0→𝐾∗0ℓ+ℓ− decays, known as 𝑅(𝐾) and 𝑅(𝐾∗), 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 fb−1. This analysis is the most sensitive lepton universality test in rare b-decays and the results obtained supersede the previous LHCb measurements of 𝑅(𝐾) and 𝑅(𝐾∗0).