Oct 2020 - Sept 2021

Internal Seminar by Sabya Chatterjee



Neutrino non-standard interactions: a possible solution to the NOvA and T2K tension


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 $\delta_{CP}$ ~ 0.8$\pi$, T2K identifies values of $\delta_{CP}$ ~ 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 |$\epsilon_{e\mu}$| ∼ |$\epsilon_{e\tau}$ | ∼ 0.2. We find that in case of normal mass ordering there is a 2.1$\sigma$ preference of the non-zero NSI coupling |$\epsilon_{e\mu}$| and 1.9$\sigma$ preference of |$\epsilon_{e\tau}$|. Remarkably, in the presence of such NSI, both experiments point towards the same common value of the standard CP-phase $\delta_{CP}$ ~ 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 |$\epsilon_{e\mu}$| and |$\epsilon_{e\tau}$| lies only at 1$\sigma$ confidence level respectively.


Zoom link:  IPPP Seminars (Friday at 2 pm UK time)


Meeting ID: 994 2012 4988