Probing Non-unitary $CP$ Violation effects in Neutrino Oscillation Experiments

TL;DR

This paper investigates the effects of non-unitary $CP$ violation in neutrino oscillations within the minimal unitarity violation scheme, analyzing sensitivities to non-unitary parameters in short baseline experiments and exploring the potential to distinguish between unitary and non-unitary $CP$ phases.

Contribution

It provides a general expression for $ u_{} ightarrow u_{ au}$ oscillation probability considering non-unitarity and studies sensitivities to non-unitary parameters in short baseline experiments, including phase effects.

Findings

Maximum sensitivity to $| ho_{}|$ at $=0$ phase for NH

Sensitivity to non-unitarity varies with $_{23}$ and hierarchy

Disentanglement of unitary and non-unitary $CP$ phases possible for $L/E<200$ km/GeV

Abstract

In the present work, we have considered minimal unitarity violation(MUV) scheme, to obtain the general expression for $\nu_{\mu}\rightarrow\nu_{\tau}$ oscillation probability, in vacuum. For this channel, we have investigated the sensitivities to non-unitary parameters $|\rho_{\mu\tau}|$ and $\omega_{\mu\tau}$ with short baseline(SBL) experiments for normal as well as inverted hierarchical neutrino masses. We also check how the sensitivity to non-unitary parameters get modified for $\theta_{23}$ above and below maximality. We find that the $3\sigma$ sensitivity towards $|\rho_{\mu\tau}|$ is maximum for non-unitary phase $\omega_{\mu\tau}=0$, whereas it is minimum for $\omega_{\mu\tau}=\pm\pi$ in case of normal hierarchy(NH). However, the sensitivity is minimum at $\omega_{\mu\tau}=0$ and maximum for $\omega_{\mu\tau}=\pm\pi$ for inverted hierarchy(IH). We observe that for unitary $CP$ phase $\delta=0$ and $\delta=\pi/2$, the sensitivity to measure non-unitarity remains same in both the cases. We, also, explore wide range of $L/E$ to forecast, in principle, the possibilities to observe $CP$-violation due to unitary($\delta$) and non-unitary($\omega_{\mu\tau}$) phases. We find that the both phases can be disentangled, in principle, from each other, for the $L/E$ range less than 200 km/GeV for $\nu_{\mu}\rightarrow\nu_{\tau}$ channel.