First measurement of electron neutrino appearance in NOvA

TL;DR

This paper reports the first measurement of electron neutrino appearance in the NOvA experiment, observing a significant excess of events that provides insights into neutrino oscillation parameters.

Contribution

It presents the first search for $ u_ o u_e$ transitions with new experimental data and analysis, advancing understanding of neutrino oscillations and CP violation.

Findings

Observed 6 events with a background of 0.99 in primary analysis.

Detected a 3.3σ excess of events, indicating potential neutrino oscillation effects.

Disfavors certain CP-violating phase ranges at 90% confidence level.

Abstract

We report results from the first search for $\nu_\mu\to\nu_e$ transitions by the NOvA experiment. In an exposure equivalent to $2.74\times10^{20}$ protons-on-target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of $0.99\pm0.11$ (syst.) events based on the Near Detector measurement. A secondary analysis observes 11 events with a background of $1.07\pm0.14$ (syst.). The $3.3\sigma$ excess of events observed in the primary analysis disfavors $0.1\pi < \delta_{CP} < 0.5\pi$ in the inverted mass hierarchy at the 90% C.L.