Nonmaximal neutrino mixing at NOνA from nonstandard interactions

Muon neutrino disappearance measurements at NOνA suggest that maximal θ23 is excluded at the 2.6σ CL. This is in mild tension with T2K data which prefer maximal mixing. Considering that NOνA has a much longer baseline than T2K, we point out that the apparent departure from maximal mixing in NOνA may be a consequence of nonstandard neutrino propagation in matter.