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

Abstract

Since neutrino oscillation was observed, several experiments have been built to measure its parameters. NO$\nu$A and T2K are two long-baseline experiments dedicated to measuring mainly the mixing angle ${\theta }_{23}$, the charge-parity conjugation phase ${\delta }_{\mathrm{CP}}$, 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$\nu$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$\nu$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 ${\delta }_{\mathrm{CP}}\pm \varphi =1.5\pi$ being a possible source of violation of charge-parity symmetry.

Comments: Accepted for publication in PRD