Neutrino mass ordering obfuscated by the NSI

TL;DR

This paper investigates how non-standard neutrino interactions, especially flavor-changing types, can obscure the determination of neutrino mass ordering, challenging current experimental indications of a normal hierarchy.

Contribution

It demonstrates that non-standard interactions can significantly affect neutrino mass ordering measurements, potentially hiding the true hierarchy in experimental data.

Findings

NSI can obscure the normal mass ordering indication.

Flavor-changing NSI involving e-tau flavors can eliminate current NO signals.

Standard 3-flavor framework results are altered by NSI effects.

Abstract

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.