New physics analysis of $Λ_b\to (Λ^*(\to pK^-), Λ(\to pπ))(μ^{+}μ^{-},\,ν\barν)$ baryonic decays under SMEFT framework

Abstract: The di-leptons and di-neutrinos observed in the final states of flavor-changing neutral b decays provide an ideal platform for probing physics beyond the standard model. Although the latest measurements of $R_{K^{(*)}}$ agree well with the standard model prediction, there exists several other observables such as $P_5^{\prime}$, $\mathcal{B}(B_s\to \phi \mu^{+}\mu^{-})$ and $\mathcal{B}(B_s\to \mu^{+}\mu^{-})$ in $b\to s \ell\ell$ transition decays that shows deviation from the standard model prediction. Similalry, very recently Belle II collaboration reported a more precise upper bound of $\mathcal{B}(B\to K^+\nu\bar{\nu}) < 4.1\times 10^{-5}$ by employing a new inclusive tagging approach and it also deviates from the standard model expectation. The $b\to s l^{+}l^{-}$ and $b\to s\nu\bar{\nu}$ transition decays are related not only in the standard model but also in beyond the standard model physics due to $SU(2)_L$ gauge symmetry, and can be most effectively investigated using the standard model effective field theory formalism. Additionally, the $b\to s\nu\bar{\nu}$ decay channels are theoretically cleaner than the corresponding $b\to s l^{+}l^{-}$ decays, as these processes do not get contributions from non-factorizable corrections and photonic penguin contributions. In this context, we study $\Lambda_b\to (\Lambda^*(\to pK^-), \Lambda(\to p\pi))({\mu}^{+}\mu^{-},\,\nu\bar{\nu})$ baryonic decays undergoing $b\to s \ell^{+}\ell^{-}$ and $b\to s\nu\bar{\nu}$ quark level transitions in a standard model effective field theory formalism. We give predictions of several observables pertaining to these decay channels in the standard model and in case of several new physics scenarios.