We report the first measurement of the neutrino-oxygen neutral-current quasielastic (NCQE) cross section. It is obtained by observing nuclear deexcitation γ rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to 3.01×1020 protons on target. By selecting only events during the T2K beam window and with well-reconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the 4-30 MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background is primarily nonquasielastic neutral-current interactions and has only 1.2 events from natural radioactivity. The flux-averaged NCQE cross section we measure is 1.55×10-38cm2 with a 68% confidence interval of (1.22,2.20)×10-38cm2 at a median neutrino energy of 630 MeV, compared with the theoretical prediction of 2.01×10-38cm2.
Publication Source (Journal or Book title)
Physical Review D - Particles, Fields, Gravitation and Cosmology
Abe, K., Adam, J., Aihara, H., Akiri, T., Andreopoulos, C., Aoki, S., Ariga, A., Ariga, T., Assylbekov, S., Autiero, D., Barbi, M., Barker, G., Barr, G., Bass, M., Batkiewicz, M., Bay, F., Bentham, S., Berardi, V., Berger, B., Berkman, S., Bertram, I., Bhadra, S., Blaszczyk, F., Blondel, A., Bojechko, C., Bordoni, S., Boyd, S., & Brailsford, D. (2014). Measurement of the neutrino-oxygen neutral-current interaction cross section by observing nuclear deexcitation γ rays. Physical Review D - Particles, Fields, Gravitation and Cosmology, 90 (7) https://doi.org/10.1103/PhysRevD.90.072012