Nuclear effects on tau lepton polarization in charged current deep inelastic $\nu_\tau/\bar\nu_\tau-A$ scattering

TL;DR

This paper investigates how nuclear effects influence tau lepton polarization in charged current deep inelastic scattering from nucleons and nuclei, relevant for experiments like IceCube and DUNE.

Contribution

It provides a detailed analysis of tau polarization considering both free nucleon and nuclear medium effects, including target mass corrections and spectral functions.

Findings

Nuclear medium effects significantly alter tau polarization predictions.

Differential cross sections are computed with NLO parton evolution and nuclear corrections.

Results are relevant for interpreting tau signals in neutrino experiments.

Abstract

We have studied the tau-lepton polarization in the charged current $\nu_\tau/\bar\nu_\tau$ induced deep inelastic scattering (DIS) from the free nucleon as well as off the nuclear targets that are being used in ongoing and proposed experiments such as IceCube, DUNE, etc. For the free nucleon target, the differential scattering cross sections are obtained by taking into account the non-perturbative effect like target mass corrections (TMC) and the perturbative effect like the evolution of the parton densities at the next-to-leading order (NLO) in the four flavor $\overline{\textrm{MS}}-$scheme. In the case of nucleons bound inside a nuclear target, we have incorporated the nuclear medium effects such as Fermi motion, binding energy and nucleon correlations, through the use of nucleon spectral function. We shall present the results for the differential scattering cross sections and the longitudinal and transverse components of the tau-lepton polarization assuming time reversal invariance.