Abe, K. and Adam, J. and Aihara, H. and Akiri, T. and Andreopoulos, C. and Aoki, S. and Ariga, A. and Ariga, T. and Assylbekov, S. and Autiero, D. and Barbi, M. and Barker, G. J. and Barr, G. and Bass, M. and Batkiewicz, M. and Bay, F. and Bentham, S. W. and Berardi, V. and Berger, B. E. and Berkman, S. and Bertram, I. and Bhadra, S. and Blaszczyk, F. d. M. and Blondel, A. and Bojechko, C. and Bordoni, S. and Boyd, S. B. and Brailsford, Dominic and Bravar, A. and Bronner, C. and Buchanan, N. and Calland, R. G. and Caravaca Rodriguez, J. and Cartwright, S. L. and Castillo, R. and Catanesi, M. G. and Cervera, A. and Cherdack, D. and Christodoulou, G. and Clifton, A. and Coleman, J. and Dealtry, Thomas and Finch, A. J. and Grant, N. and Kormos, L. L. and Lamont, I. and O'Keeffe, H. M. and Ratoff, P. N. and Reeves, M. and Southwell, L. (2014) Precise Measurement of the Neutrino Mixing Parameter θ_{23} from Muon Neutrino Disappearance in an Off-axis Beam. Physical review letters, 112 (18): 181801. ISSN 0031-9007
Abstract
New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter theta_{23}. Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57 x 10^{20} protons on target, T2K has fit the energy-dependent nu_mu oscillation probability to determine oscillation parameters. Marginalizing over the values of other oscillation parameters yields sin^2 (theta_{23}) = 0.514 +0.055/-0.056 (0.511 +- 0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Delta m^2_{32} = (2.51 +- 0.10) x 10^{-3} eV^2/c^4 (inverted hierarchy: Delta m^2_{13} = (2.48 +- 0.10) x 10^{-3} eV^2/c^4). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty.