# Probing Left-Right Seesaw using Beam Polarization at an $e^+e^-$ Collider

## TL;DR

This paper demonstrates how beam polarization at future electron-positron colliders can distinguish low-scale seesaw neutrino models and probe new parameter spaces, enhancing the understanding of neutrino mass mechanisms.

## Contribution

It introduces a method to use beam polarization to differentiate seesaw models and explore previously inaccessible parameter regions at colliders.

## Key findings

- Beam polarization enhances heavy neutrino production cross section.
- Maximum enhancement depends on light-heavy neutrino mixing.
- New parameter space of left-right seesaw models can be probed.

## Abstract

We show that the longitudinal beam polarization option at a future electron-positron collider provides an unambiguous distinction between low-scale seesaw models of neutrino mass. This is possible due to the fact that the pair production cross section of the heavy neutrinos in seesaw models is sensitive to the polarization of the initial lepton beams, and for a suitable choice of the polarization, shows a clear enhancement over the unpolarized cross section. More interestingly, the choice of the beam polarization for which the enhancement is maximum is governed by the size of the light-heavy neutrino mixing parameter. We also find that using this effect, one can probe a previously uncharted parameter space of the left-right seesaw model, which is complementary to the existing searches at both energy and intensity frontiers.