Speaker
Description
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 $\theta_{23}$ octant) that renders the mass hierarchy, octant, and CP phase unknowable. Even with a combination of NO$\nu$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 $\epsilon_{e\mu}$. If $\epsilon_{e\tau}$ is nonzero, or the diagonal NSI parameter $\epsilon_{ee}$ is ${\cal O}(1)$, a wrong determination of the mass hierarchy and of CP violation can occur at DUNE. The octant degeneracy can be further complicated by $\epsilon_{e\tau}$, but is not
affected by $\epsilon_{ee}$.
