New physics analysis of Λb→(Λ∗(→pK−),Λ(→pπ))(μ+μ−, ννˉ)\Lambda_b\to (\Lambda^*(\to pK^-), \Lambda(\to p\pi))({\mu}^{+}\mu^{-},\,\nu\bar{\nu}) baryonic decays under SMEFT framework

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.Comment: 22 Pages, 6 Figures, 13 Table

Perturbative Bottom-up Approach for Neutrino Mass Matrix in Light of Large \theta_{13} and Role of Lightest Neutrino Mass

We discuss the role of lightest neutrino mass (m_0) in the neutrino mass matrix, defined in a flavor basis, through a bottom-up approach using the current neutrino oscillation data. We find that if m_0 < 10^{-3} eV, then the deviation \delta M_\nu in the neutrino mass matrix from a tree-level, say tribimaximal neutrino mass matrix, does not depend on m_0. As a result \delta M_\nu's are exactly predicted in terms of the experimentally determined quantities such as solar and atmospheric mass squared differences and the mixing angles. On the other hand for m_0 \gsim 10^{-3} eV, \delta M_\nu strongly depends on m_0 and hence can not be determined within the knowledge of oscillation parameters alone. In this limit, we provide an exponential parameterization for \delta M_\nu for all values of m_0 such that it can factorize the m_0 dependency of \delta M_\nu from rest of the oscillation parameters. This helps us in finding \delta M_\nu as a function of the solar and atmospheric mass squared differences and the mixing angles for all values of m_0. We use this information to build up a model of neutrino masses and mixings in a top-down scenario which can predict large \theta_{13} perturbatively.Comment: 26 pages, 42 eps figures, revtex (references are added, more discussions are added in section-III