Probing non-unitary CP violation effects in neutrino oscillation experiments

Abstract

In the present work, we have considered minimal unitarity violation scheme to obtain the general expression for $$\nu _{\mu }\rightarrow \nu _{\tau }$$ oscillation probability in vacuum and matter. For this channel, we have investigated the sensitivities of short baseline experiments to non-unitary parameters $$|\rho _{\mu \tau }|$$ and $$\omega _{\mu \tau }$$ for normal as well as inverted hierarchical neutrino masses and $$\theta _{23}$$ being above or below maximality. We find that for normal hierarchy, the $$3\sigma$$ sensitivity of $$|\rho _{\mu \tau }|$$ is maximum for non-unitary phase $$\omega _{\mu \tau }=0$$ whereas it is minimum for $$\omega _{\mu \tau }=\pm \pi$$ . For inverted hierarchy, the sensitivity is minimum at $$\omega _{\mu \tau }=0$$ and maximum for $$\omega _{\mu \tau }=\pm \pi$$ . We observe that the sensitivity to measure non-unitarity remains unaffected for unitary CP phase $$\delta =0$$ or $$\delta =\pi /2$$ . We have, also, explored wide spectrum of L/E ratio to investigate 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 $$L/E<200$$ km/GeV.