First measurement of muon-neutrino disappearance in NOvA

This paper reports the first measurement using the NOvA detectors of ?µ disappearance in a ?µ beam. The analysis uses a 14 kton-equivalent exposure of 2.74×1020 protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure ?m232=(2.52+0.20-0.18)×10-3??eV2 and sin2?23 in the range 0.38–0.65, both at the 68% confidence level, with two statistically degenerate best-fit points at sin2?23=0.43 and 0.60. Results for the inverted mass hierarchy are also presented.