# Neutrino elastic scattering on polarized electrons as a tool for probing the neutrino nature

## TL;DR

This paper explores how polarized electron targets and neutrino scattering experiments can distinguish between Dirac and Majorana neutrinos, especially through azimuthal asymmetries and interference effects involving standard and non-standard interactions.

## Contribution

It introduces a model-independent method using polarized electron targets to differentiate neutrino types via elastic scattering and interference effects.

## Key findings

- Azimuthal asymmetries reveal neutrino nature and TRSV interactions.
- Interference between standard and exotic interactions affects electron recoil distributions.
- Polarized targets enhance sensitivity to non-standard neutrino interactions.

## Abstract

Possibility of using the polarized electron target (PET) for testing the neutrino nature is considered. One assumes that the incoming electron neutrino ($\nu_e$) beam is the superposition of left chiral states with right chiral ones. Consequently the non-vanishing transversal components of $\nu_e$ spin polarization may appear, both T-even and T-odd. $\nu_e$s are produced by the low energy monochromatic (un)polarized emitter located at a near distance from the hypothetical detector which is able to measure both the azimuthal angle and polar angle of the recoil electrons, and/or also the energy of the outgoing electrons with a high resolution. A detection process is the elastic scattering of $\nu_e$s (Dirac or Majorana) on the polarized electrons. Left chiral (LC) $\nu_e$s interact mainly by the standard $V - A$ interaction, while right chiral (RC) ones participate only in the non-standard $V + A$, scalar $S_R$, pseudoscalar $P_R$ and tensor $T_R$ interactions. All the interactions are of flavour-conserving type (FC). We show that a distinction between the Dirac and the Majorana $\nu_e$ s is possible both for the longitudinal and the transversal $\nu_e$ polarizations. In the first case a departure from the standard prediction of the azimuthal asymmetry of recoil electrons is caused by the interferences between the non-standard complex S and T couplings. Such a deviation would indicate the Dirac $\nu_e$ nature and the presence of time reversal symmetry violation (TRSV) interactions. In the second case the azimuthal asymmetries, polar distribution and energy spectrum of scattered electrons are sensitive to the interference terms between the standard and exotic interactions, proportional to the various angular correlations. Our model-independent study is carried out for the flavour $\nu_e$ eigenstates in the relativistic $\nu_e$ limit.