On possibility of time reversal symmetry violation in neutrino elastic scattering on polarized electron target

TL;DR

This paper explores how elastic scattering of low-energy electron neutrinos on polarized electrons can be used to test for violations of time reversal symmetry, considering both standard and exotic interactions.

Contribution

It introduces a model-independent method to detect time reversal symmetry violation in neutrino-electron scattering using polarized targets and interference effects.

Findings

Azimuthal asymmetry of recoil electrons depends on TRS violation.

Energy spectrum and angular distributions are sensitive to exotic couplings.

Maximal asymmetry varies with the azimuthal angle of neutrino spin polarization.

Abstract

In this paper, we indicate a possibility of utilizing the elastic scattering of the Dirac low energy ($\sim 1$ MeV) electron neutrinos ($\nu_e$'s) on the polarized electron target (PET) in testing the time reversal symmetry violation (TRSV). We consider a scenario in which the incoming $\nu_e$ beam is the superposition of left chiral (LC) and right chiral (RC) states. LC $\nu_e$'s interact mainly by the standard $V - A$, while RC ones are only detected by the exotic $V + A$ and $S_R, P_R, T_R$ interactions. One assumes that the spin polarization vector of the initial $\nu_e$'s is turned aside from the $\nu_e$ momentum, and due to this the non-vanishing transversal component of the $\nu_e$ spin polarization appears. We compute the differential cross section as a function of the recoil electron azimuthal angle and scattered electron energy, and show how the interference terms between standard $V-A$ and exotic $S_R, P_R, T_R$ couplings depend on the various angular correlations among the transversal $\nu_e$ spin polarization, the polarization of the electron target, the incoming neutrino momentum and the outgoing electron momentum in the limit of relativistic $\nu_e$. We illustrate how the maximal value of recoil electrons azimuthal asymmetry and the asymmetry axis location of outgoing electrons depend on the azimuthal angle of the transversal component of the $\nu_e$ spin polarization, both for the time reversal symmetry conservation (TRSC) and TRSV. Next, we display that the electron energy spectrum and polar angle distribution of the recoil electrons are also sensitive to the interference terms between $V - A$ and $S_R, P_R, T_R$ couplings, proportional to the T-even and T-odd angular correlations. Our model-independent analysis is carried out for the flavor $\nu_e$'s.