Speaker
Description
The recent measurements on $R_D$, $R_{D^*}$ and $R_{J/\psi}$ by BaBar, Belle and LHCb experiments, which deviate substantially from their Standard Model predictions indicate that the notion of lepton flavour universality (LFU) is violated in the weak charged-current processes, mediated through $b \to c \ell \bar \nu_\ell$ transitions. These intriguing results hint towards the possible implication of new physics in $ b \to c \tau \bar \nu$ transition. This, in turn, opens up another avenue, i.e., $ b \bar b \to \tau \bar \tau$ processes, to look for new physics, i.e., the new physics contributions to $ b \to c \tau \bar \nu$ process would necessarily modify the $ b \bar b \to \tau \bar \tau$ transitions. In this context, we study the implications of LFU violating new physics scenarios of ratio of branching fractions of leptonic $\Upsilon \equiv \Upsilon(ns) (n=1,2,3)$ decays, i.e., $R_{\Upsilon}(ns)= Br(\Upsilon(ns) \to \tau \bar{\tau})/ Br(\Upsilon(ns) \to \mu \bar{\mu})$. We find that $ R_{\Upsilon}(ns)$ values deviate significantly from their standard model predictions due to the impact of new physics.
| Session | Quark and Lepton Flavour Physics |
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