Probing new physics in semileptonic ${\Lambda }_b$ decays

Abstract

In recent times, several hints of lepton non-universality have been observed in semileptonic $B$ meson decays, both in the charged-current ($b\to cl{\bar{\nu }}_l$) and neutral-current ($b\to sll$) transitions. Motivated by these intriguing results, we perform a model independent analysis of the semileptonic ${\Lambda }_b$ decays involving the quark level transitions $b\to (u,c)l{\nu }_l$, in order to scrutinize the nature of new physics. We constrain the new parameter space by using the measured branching ratios of $B_{c,u}^{+}\to {\tau }^{+}{\nu }_{\tau }$, $B\to \pi \tau {\nu }_{\tau }$ processes and the existing experimental results on $R_{D^{(\ast )}}$, $R_{J/\psi }$ and $R_{\pi }^l$ parameters. Using the constrained parameters, we estimate the branching ratios, forward backward asymmetries, hadron and lepton polarization asymmetries of the ${\Lambda }_b\to ({\Lambda }_c,p)l{\nu }_l$ processes. Moreover, we also examine whether there could be any lepton universality violation in these decay modes.

Comments: 33 pages, 18 figures, to appear in PRD