Neutrino Non-standard Interactions: A Solution to the NO \(\nu \) A and T2K Tension

The current data from the NO \(\nu \) A and T2K accelerator experiments show a tension in determining the standard CP-phase \(\delta _{CP}\) for neutrino normal ordering. NOvA measures \(\delta _{CP} \sim 0.8 \pi \) , while T2K prefers \(\delta _{CP}\sim 1.4 \pi \) . We show that this tension can be resolved by considering the existence of neutral-current non-standard interactions (NSI) involving \(e-\mu \) or \(e-\tau \) sectors with couplings \(|\varepsilon _{e\mu }| \sim |\varepsilon _{e\tau }| \sim 0.2\) . In the presence of such NSI, both experiments point towards a common value of \(\delta _{CP} \sim 3 \pi /2\) , indicating maximal CP-violation in the standard \(3\nu \) framework. The best fit values of the new CP-phases \(\phi _{e\mu }\) or \(\phi _{e\tau }\) are also close to \(\sim 3 \pi /2\) , suggesting maximal CP-violation in the NSI sector.