Probing new physics with polarized $\tau$ and $\Lambda_c$ in quasielastic $\nu_{\tau}\!+\!n\!\to\! \tau^-\!+\!\Lambda_c$ scattering process

TL;DR

This paper investigates the potential of using polarized $ au$ and $\Lambda_c$ in quasielastic $ u_{ au} + n o au^- + \Lambda_c$ scattering to probe new physics beyond the Standard Model, addressing the limitations of semitauonic decays.

Contribution

It introduces a novel approach to search for new physics via polarization measurements in quasielastic neutrino scattering, considering various NP scenarios and analyzing form factor uncertainties.

Findings

Polarization observables can reveal NP signals.

Form factor uncertainties pose significant challenges.

Differential cross sections are sensitive to NP effects.

Abstract

The absence of semitauonic decays of charmed hadrons makes the decay processes mediated by the quark-level $c\to d \tau^+ \nu_{\tau}$ transition inadequate for probing a generic new physics (NP) with all kinds of Dirac structures. To fill in this gap, we consider in this paper the quasielastic neutrino scattering process $\nu_{\tau}+n\to \tau^-+\Lambda_c$, and propose searching for NP through the polarizations of the $\tau$ lepton and the $\Lambda_c$ baryon. In the framework of a general low-energy effective Lagrangian, we perform a comprehensive analysis of the (differential) cross sections and polarization vectors of the process both within the Standard Model and in various NP scenarios, and scrutinize possible NP signals. We also explore the influence on our findings due to the uncertainties and the different parametrizations of the $\Lambda_c \to N$ transition form factors, and show that they have become one of the major challenges to further constrain possible NP through the quasielastic scattering process.