Precise Measurement of the Neutrino Mixing Parameter \theta_{23} from Muon Neutrino Disappearance in an Off-axis Beam

• Published in: arXiv.org 2014-05
• Main Authors: T2K Collaboration, Ariga, A, Assylbekov, S, Bay, F, Berkman, S, Bojechko, C, Cherdack, D, Clifton, A, Coleman, S J, Collazuol, G, Cremonesi, L, Danko, I, Das, R, Davis, S, De Rosa, G, Dealtry, T, Dennis, S R, Densham, C, Duboyski, T, Dumarchez, J, Dziewiecki, M, Ereditato, A, Finch, A J, Fujii, Y, Furmanski, A P, Gilje, K, Haesler, A, Hansen, D, Hasegawa, T, Hastings, N C, Hiraki, T, Horikawa, S, Ieki, K, Jacob, A, Johnson, R A, Jo, J H, Kajita, T, Kanazawa, Y, Karlen, D, Karpikov, I, Kielczewska, D, Kitching, P, Kobayashi, T, Kolaceke, A, Koseki, K, Kumaratunga, S, Kutter, T, Lagoda, J, Laihem, K, Magaletti, L, Marino, A D, Martin, J F, Maruyama, T, Marzec, J, Matveev, V, McGrew, C, Mijakowski, P, Miller, C A, Mine, S, Murakami, A, Nakamura, K, O'Keeffe, H M, Payne, D, Perevozchikov, O, Przewlocki, P, Ratoff, P N, Ravonel, M, Rodrigues, P A, Ruterbories, D, Sacco, R, Scott, M, Sekiguchi, T, Sekiya, H, Shiozawa, M, Shustrov, Y, Sobczyk, J T, Sobel, H, Suda, Y, Suzuki, S Y, Szeglowski, T, Tanaka, H K, Terri, R, Thompson, L F, Thorley, A, Tobayama, S, Toki, W, Uchida, Y, Ueno, K, Vagins, M, Waldron, A V, Wendell, R, Wilkes, R J, Wilkinson, C, Williamson, Z, Wongjirad, T, Yamamoto, K, M Yu, Zalewska, A, Zalipska, J, Zmuda, J
• Format: Article
• Language: English
• Subjects: Experiments; Neutrino beams; Neutrinos; Parameter uncertainty; Particle physics; Statistical analysis
• ISSN: 2331-8422

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.