Alleviating the present tension between T2K and NO$ν$A with nonstandard neutrino interactions

Abstract

Since neutrino oscillation was observed, several experiments have been built to measure its parameters. NO$ν$A and T2K are two long-baseline experiments dedicated to measuring mainly the mixing angle $θ_{23}$, the charge-parity conjugation phase $δ_{\rm CP}$, and the mass ordering. However, there is a tension in current data. The T2K allowed region is in conflict with the region allowed by NO$ν$A. We propose a nonstandard charged current interaction (CC-NSI) in neutrino production to relieve this tension. The CC-NSI is computed through quantum field theory (QFT) formalism, where we derive perturbative analytical formulae considering CC-NSI in the pion decay. Within this new approach, we can alleviate NO$ν$A and T2K tension for a CC-NSI complex parameters of order $10^{-3}$. We show the new phase has a degeneracy to the Dirac CP phase of the form $δ_{\rm CP} \pm ϕ= 1.5π$ being a possible source of violation of charge-parity symmetry.