Test of lepton universality in beauty-quark decays

TL;DR

This paper reports evidence of lepton universality violation in beauty-quark decays, challenging the Standard Model and suggesting potential new physics beyond current theories.

Contribution

It provides the first evidence of lepton universality breaking in beauty-quark decays with a significance of 3.1 sigma, based on LHCb data.

Findings

Evidence for lepton universality violation at 3.1 sigma

Decay processes involving beauty mesons show different behaviors for electrons and muons

Implication of possible new fundamental interactions beyond the Standard Model

Abstract

The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the Standard Model, such as a new fundamental interaction between quarks and leptons.