First measurement of muon-neutrino disappearance in NOvA

This paper reports the first measurement using the NOvA detectors of nu(mu) disappearance in a nu(mu) beam. The analysis uses a 14 kton-equivalent exposure of 2.74 x 10(20) protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure Delta m(32)(2) = (2.52(-0.18)(+0.20)) x 10(-3) eV(2) and sin(2) theta(23) in the range 0.38-0.65, both at the 68% confidence level, with two statistically degenerate best-fit points at sin(2) theta(23) = 0.43 and 0.60. Results for the inverted mass hierarchy are also presented