Assessing lepton flavor universality violations in semileptonic decays

Abstract

In light of recent measurements suggesting potential lepton flavor universality violations in semileptonic decays at collider experiments, this article provides a concise study of tree- and loop-level B-hadron semileptonic decays, \(b \rightarrow c l \nu _l\) and \(b \rightarrow s l^+ l^-\). We provide predictions for lepton flavor violating observables, \({\mathcal {R}}_{J/\psi }\) and \({\mathcal {R}}_{\eta _c}\), across the entire \(q^2\) range. Our study employs the Relativistic Independent Quark Model (RIQM), highlighting a model-dependent approach to these observables. We compare our model’s predictions with existing lattice predictions, demonstrating the strong applicability of the RIQM framework in describing \(B_c\) decays. Additionally, we reassess global averages for \({\mathcal {R}}_{D(D^*)}\) and \({\mathcal {R}}_{K(K^*)}\) in semileptonic transitions. With the upcoming experimental upgrades and the anticipated Run 3 data on \(B_c\) meson decays, rapid confirmation of these quantities could indicate significant evidence of physics beyond the Standard Model, thereby opening new pathways for understanding the complex flavor dynamics in B meson decays.