Neutrino mass ordering obfuscated by the NSI

Determination of the neutrino mass ordering (NMO) is one of the biggest priorities in the intensity frontier of high energy particle physics. To accomplish that goal a lot of efforts are being put together with the atmospheric, solar, reactor, and accelerator neutrinos. In the standard 3-flavor framework, NMO is defined to be normal if $m_1<m_2<m_3$, and inverted if $m_3<m_1<m_2$, where $m_1$, $m_2$, and $m_3$ are the masses of the three neutrino mass eigenstates $\nu_1$, $\nu_2$, and $\nu_3$ respectively. Interestingly, two long-baseline experiments T2K and NO$\nu$A are playing a leading role in this direction and provide a $\sim2.4\sigma$ indication in favor of normal ordering (NO) which we find in this work. In addition, we examine how the situation looks like in presence of non-standard interactions (NSI) of neutrinos with a special focus on the non-diagonal flavor changing type $\varepsilon_{e\tau}$ and $\varepsilon_{e\mu}$. We find that the present indication of NO in the standard 3-flavor framework gets completely vanished in the presence of NSI of the flavor changing type involving the $e-\tau$ flavors.