Measurement of the Neutrino Mixing Angle θ_(23) in NOvA
This Letter reports new results on muon neutrino disappearance from NOvA, using a 14 kton detector equivalent exposure of 6.05×10^(20) protons on target from the NuMI beam at the Fermi National Accelerator Laboratory. The measurement probes the muon-tau symmetry hypothesis that requires maximal θ_(23) mixing (θ_(23)=π/4). Assuming the normal mass hierarchy, we find Δm^2_(32)=(2.67±0.11)×10^(−3) eV^2 and sin^2 θ_(23) at the two statistically degenerate values 0.404^(+0.030)_(−0.022) and 0.624^(+0.022)_(−0.030), both at the 68% confidence level. Our data disfavor the maximal mixing scenario with 2.6σ significance.
© 2017 American Physical Society. Received 23 January 2017; published 10 April 2017. This work was supported by the U.S. Department of Energy; the U.S. National Science Foundation; the Department of Science and Technology, India; the European Research Council; the MSMT CR, GA UK, Czech Republic; the RAS, RMES, and RFBR, Russia; CNPq and FAPEG, Brazil; and the state and University of Minnesota. We are grateful for the contributions of the staffs of the University of Minnesota module assembly facility, Argonne National Laboratory, and Fermilab. Fermilab is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the U.S. DOE.
Submitted - 1701.05891.pdf
Published - PhysRevLett.118.151802.pdf