Speaker
Description
The latest data of the two long-baseline accelerator experiments NOνA and T2K, analysed in the standard 3-flavor scenario, display a discrepancy. A mismatch in the determination of the standard CP-phase $\delta_{CP}$ extracted by the two experiments is evident in the normal neutrino mass ordering. While NOνA prefers values close to $\delta_{CP}\sim 0.8\pi$, T2K identifies values of $\delta_{CP}\sim 1.4\pi$. Such two estimates are in disagreement at more than 90% C.L. for 2 d.o.f.. We show that such a tension can be resolved if one hypothesizes the existence of complex neutral-current non-standard interactions (NSI) of the flavor changing type involving the $𝑒−\mu$ or the $𝑒−\tau$ sectors with couplings |$\varepsilon_{e\mu}$| ∼ |$\varepsilon_{e\tau}$| ∼ 0.2. We find that in case of normal mass ordering there is a 2.1$\sigma$ preference of the non-zero NSI coupling |$\varepsilon_{e\mu}$| and 1.9$\sigma$ preference of |$\varepsilon_{e\tau}$|. Remarkably, in the presence of such NSI, both experiments point towards the same common value of the standard CP-phase $\delta_{CP} \sim 3\pi/2$. Our analysis also highlights an intriguing preference for maximal CP-violation in the non-standard sector with the dynamical NSI CP-phases having best fit close to $\phi_{e\mu}$ ~ $\phi_{e\tau}$ ~ $3\pi/2$. Although not very strong this might be a possible sign of physics beyond the Standard Model. It is also worth to mention that in case of inverted ordering the preference of non-zero NSI couplings |\varepsilon_{e\mu}| and |\varepsilon_{e\tau}| lies only at 1$\sigma$ confidence level respectively.
