Lepton flavor non-universality in TAU sector

Abstract

Recently, the LHCb experiment has observed lepton flavor non-universality parameters <i>R_K</i> and <i>R_K*</i> for exclusive <i>B → (K, K*)l<Sup>+</Sup>l<Sup>-</Sup></i>i> decay modes, respectively. These <i>R_K</i> and <i>R_K*</i> are the ratios of branching fraction of µ-channel to <i>e</i>-channel for the corresponding decay modes and are found to have ~3 σ deviation from their standard model (SM) values. Here, we are interested to study the exclusive decay mode <i>B → Kτ<Sup>+</Sup>τ<Sup>-</Sup></i> and predict the branching ratio in the SM and also in one new physics model, i.e., the non-universal <i>Z'</i> model. We also look towards the ratios of branching fractions of <i>τ</i>-channel to <i>µ</i>- and <i>e</i>- channels, i.e., <i>R</i><img src='http://nopr.niscair.res.in/jinfo/papsep1.gif' border=0> and <i>R</i><img src='http://nopr.niscair.res.in/jinfo/papsep2.gif' border=0> respectively, to find out whether any lepton flavor non-universality is present in sector. As the decay channels like <i>B → K, K*</i> having leptons in their final states are still out of the experimental reach, so we hope our predictions could give a new approach for the search of τ-channels as well as the existence of lepton flavor non-universality.