Searching for Novel Neutrino Interactions at NOvA and Beyond in Light of Large theta_13

TL;DR

This paper explores the potential of upcoming long-baseline neutrino experiments, especially NOvA and LBNE, to detect nonstandard neutrino interactions in light of the large theta_13 angle, highlighting their sensitivity and interpretative challenges.

Contribution

It demonstrates that large theta_13 enhances NSI sensitivity in long-baseline experiments and discusses how these experiments can identify or be confounded by NSI effects.

Findings

NOvA can detect ~3sigma deviations due to NSI in some parameter regions

NSI can cause ambiguities in interpreting CP violation and mass hierarchy

Longer baseline LBNE can help resolve degeneracies caused by NSI

Abstract

We examine the prospects of probing nonstandard interactions (NSI) of neutrinos in the e-tau sector with upcoming long-baseline nu_mu -> nu_e oscillation experiments. First conjectured decades ago, neutrino NSI remain of great interest, especially in light of the recent 8B solar neutrino measurements by SNO, Super-Kamiokande, and Borexino. We observe that the recent discovery of large theta_13 implies that long-baseline experiments have considerable NSI sensitivity, thanks to the interference of the standard and new physics conversion amplitudes. In particular, in some parts of NSI parameter space, the upcoming NOvA experiment will be sensitive enough to see ~ 3sigma deviations from the SM-only hypothesis. On the flip side, NSI introduce important ambiguities in interpreting NOvA results as measurements of CP-violation, the mass hierarchy and the octant of theta_23. In particular, observed CP violation could be due to a phase coming from NSI, rather than the vacuum Hamiltonian. The proposed LBNE experiment, with its longer ~ 1300 km baseline, may break many of these interpretative degeneracies.