New physics effects on Λb→Λc*τν¯τ decays

Abstract

We benefit from a recent lattice determination of the full set of vector, axial and tensor form factors for the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{*}(2595)\ensuremath{\tau}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ and ${\mathrm{\ensuremath{\Lambda}}}_{c}^{*}(2625)\ensuremath{\tau}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ semileptonic decays to study the possible role of these two reactions in lepton flavor universality violation studies. Using an effective theory approach, we analyze different observables that can be accessed through the visible kinematics of the charged particles produced in the tau decay, for which we consider the ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}},{\ensuremath{\rho}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ and ${\ensuremath{\mu}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ channels. We compare the results obtained in the Standard Model and other schemes containing new physics (NP) interactions, with either left-handed or right-handed neutrino operators. We find a discriminating power between models similar to the one of the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}$ decay, although somewhat hindered in this case by the larger errors of the ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{*}$ lattice form factors. Notwithstanding this, the analysis of these reactions is already able to discriminate between some of the NP scenarios and its potentiality will certainly improve when more precise form factors are available.