Lepton Flavor Universality tests in $b\to s\ell^+\ell^-$ decays at LHCb

Abstract

The electroweak sector of the Standard Model contains three generations of charged leptons $\ell^-\in\{e^-,\mu^-,\tau^-\}$ as exact replicas of each other, except for their Yukawa couplings to the Higgs that determine their masses. The Yukawas, and thereby, the masses, are not predicted but are parameters in the theory. A basic tenet in the formalism, known as lepton universality, is equality of the couplings to the electroweak gauge bosons $\{\gamma, Z, W^-\}$ among all three generations, and has mostly stood the test of time. However, precision tests in $B$ decays have recently posed serious challenges to lepton flavor universality, potentially pointing to New Physics beyond the Standard Model. In this work we summarize the latest LHCb results on lepton flavor universality tests in the $b\to s\ell^+\ell^+$ electroweak penguin sector and mention further prospects with the upgraded LHCb detector.