Probing new physics scenarios using high energy events at NOvA far detector

Abstract

NuMI Off-axis $\nu_e$ Appearance (NOvA) experiment is an ongoing long baseline neutrino oscillation experiment. The primary channels of interest are the $\nu_e$, $\bar{\nu}_e$ appearance, $\nu_\mu$, $\bar{\nu}_\mu$ disappearance channels analyzed in the energy window $1< E_\nu < 4$ GeV. However, NOvA far detector sees non-trivial high energy $\nu_e$, $\bar{\nu}_e$ events in the energy range $4 < E_\nu < 20$ GeV. These high energy events provide us with an opportunity to investigate the subleading new physics scenarios. In this context, we study the sensitivity of the NOvA experiment to constrain the non-standard interaction (NSI) parameters and environmental decoherence. We observe that by including high energy events (signal + background) the degeneracy around $\epsilon_{e\tau} \sim 1.6$ can be removed throughout the $\delta_{CP}$ and $\delta_{e\tau}$ range. Further, we examine the role of signal versus beam background events in removing this degeneracy. In addition, we constrain the decoherence parameter $\Gamma$ considering events from $1<E_\nu<20$ GeV. Later, assuming the presence of decoherence in nature we obtain the allowed regions in $\theta_{23}$ and $\delta_{CP}$ plane.