July 30, 2022 to August 6, 2022
Cliff Lodge
US/Mountain timezone

Tension between the T2K and NOvA appearance data and hints to new physics

Aug 5, 2022, 5:16 PM
Ballroom 2

Ballroom 2

Talk WG1: Neutrino Oscillation Physics WG1: Neutrino Oscillations


Ushak Rahaman (University of Johannesburg)


The tension between the T2K and NOvA long-baseline experiments arises mostly due to the mismatch in the $\nu_\mu \to \nu_e$ and ${\bar\nu}_\mu \to {\bar\nu}_e$ appearance data. Assuming vacuum oscillation as the reference point, with maximal $\theta_{23}$ and $\delta_{CP} = 0$, we compute the $\nu_e$/${\bar\nu}_e$ appearance events for each of the experiments. T2K observes a large excess in the $\nu_e$ appearance event sample compared to the expected $\nu_e$ events at the reference point, whereas NOvA observes a moderate excess. The large excess in T2K dictates that $\delta_{CP}$ be anchored at $−90^\circ$ and that $\theta_{23} > \pi/4$ with a preference for normal hierarchy (NH). The moderate excess at NOvA leads to two degenerate solutions: (a) NH, $0 < \delta_{CP} < 180^\circ$, and $\theta_{23} > \pi/4$; (b) inverted hierarchy (IH) with $−180^\circ < \delta_{CP} < 0$, and $\theta_{23} > \pi/4$. This is the main cause of tension between the two experiments. We show that beyond the standard model (BSM) physics scenarios such as non-unitary neutrino mixing, Lorentz invariance violation, and non-standard neutrino interactions, may resolve the tension.

Attendance type Virtual presentation

Primary authors

Ushak Rahaman (University of Johannesburg) Soebur Razzaque (University of Johannesburg) Sankagiri Umasankar (Indian Institute of Technology Bombay)

Presentation materials