New physics effects on $\Lambda_b\to \Lambda^*_c\tau\bar\nu_\tau$ decays

TL;DR

This paper investigates the impact of new physics on specific Lambda_b decays to excited Lambda_c states, utilizing lattice form factors and effective theory to analyze observables related to lepton flavor universality violation.

Contribution

It provides the first detailed analysis of Lambda_b to excited Lambda_c decays with lattice form factors, exploring their potential to distinguish new physics scenarios.

Findings

Standard Model and NP models show different predictions for observables.

Current lattice form factor uncertainties limit discrimination power.

Future precise form factors could enhance NP scenario discrimination.

Abstract

We benefit from a recent lattice determination of the full set of vector, axial and tensor form factors for the $\Lambda_b\to \Lambda^*_c(2595)\tau\bar\nu_\tau$ and $\Lambda^*_c(2625)\tau\bar\nu_\tau$ 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 $\pi^-\nu_\tau,\rho^-\nu_\tau$ and $\mu^-\bar\nu_\mu\nu_\tau$ 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 $\Lambda_b\to \Lambda_c$ decay, although somewhat hindered in this case by the larger errors of the $\Lambda_b\to\Lambda^*_c$ 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.