Jiajun Liao

Degeneracies in long-baseline neutrino experiments from nonstandard interactions

We study parameter degeneracies that can occur in long-baseline neutrino appearance experiments due to nonstandard interactions (NSI) in neutrino propagation. For a single off-diagonal NSI parameter, and neutrino and antineutrino measurements at a single L/E, there exists a continuous four-fold degeneracy (related to the mass hierarchy and

Perturbations to

\theta_{23}

\mu-\tau

octant) that renders the mass hierarchy, octant, and CP phase unknowable. Even with a combination of NO

symmetry in neutrino mixing

\nu

One diagonal texture or cofactor zero of the neutrino mass matrix

A and T2K data, which in principle can resolve the degeneracy, both NSI and the CP phase remain unconstrained because of experimental uncertainties. A wide-band beam experiment like DUNE will resolve this degeneracy if the nonzero off-diagonal NSI parameter is

Seesaw mechanism with four texture zeros in the neutrino Yukawa matrix

\epsilon_{e\mu}

Lorentz noninvariant oscillations of massless neutrinos are excluded

. If

Dual models of the neutrino mass spectrum

\epsilon_{e\tau}

Dark matter annihilation with s-channel internal Higgsstrahlung

is nonzero, or the diagonal NSI parameter

IceCube’s astrophysical neutrino energy spectrum from C P T violation

\epsilon_{ee}