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arXiv · 1512.02495

Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam

T2K collaboration·K. Abe·C. Andreopoulos·M. Antonova·S. Aoki·A. Ariga·S. Assylbekov·D. Autiero·M. Barbi·G. J. Barker·G. Barr·P. Bartet-Friburg·M. Batkiewicz·F. Bay·V. Berardi·S. Berkman·S. Bhadra·A. Blondel·S. Bolognesi·S. Bordoni·S. B. Boyd·D. Brailsford·A. Bravar·C. Bronner·M. Buizza Avanzini·R. G. Calland·S. Cao·J. Caravaca Rodríguez·S. L. Cartwright·R. Castillo·M. G. Catanesi·A. Cervera·D. Cherdack·N. Chikuma·G. Christodoulou·A. Clifton·J. Coleman·G. Collazuol·L. Cremonesi·A. Dabrowska·G. De Rosa·T. Dealtry·P. F. Denner·S. R. Dennis·C. Densham·D. Dewhurst·F. Di Lodovico·S. Di Luise·S. Dolan·O. Drapier·K. E. Duffy·J. Dumarchez·S. Dytman·M. Dziewiecki·S. Emery-Schrenk·A. Ereditato·T. Feusels·A. J. Finch·G. A. Fiorentini·M. Friend·Y. Fujii·D. Fukuda·Y. Fukuda·A. P. Furmanski·V. Galymov·A. Garcia·S. G. Giffin·C. Giganti·F. Gizzarelli·M. Gonin·N. Grant·D. R. Hadley·L. Haegel·M. D. Haigh·P. Hamilton·D. Hansen·T. Hara·M. Hartz·T. Hasegawa·N. C. Hastings·T. Hayashino·Y. Hayato·R. L. Helmer·M. Hierholzer·A. Hillairet·A. Himmel·T. Hiraki·S. Hirota·M. Hogan·J. Holeczek·S. Horikawa·F. Hosomi·K. Huang·A. K. Ichikawa·K. Ieki·M. Ikeda·J. Imber·J. Insler·R. A. Intonti·T. J. Irvine
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Abstract

T2K reports its first measurements of the parameters governing the disappearance of $\bar{\nu}_\mu$ in an off-axis beam due to flavor change induced by neutrino oscillations. The quasimonochromatic $\bar{\nu}_\mu$ beam, produced with a peak energy of 0.6 GeV at J-PARC, is observed at the far detector Super-Kamiokande, 295 km away, where the $\bar{\nu}_\mu$ survival probability is expected to be minimal. Using a dataset corresponding to $4.01 \times 10^{20}$ protons on target, $34$ fully contained $\mu$-like events were observed. The best-fit oscillation parameters are $\sin^2 (\bar{\theta}_{23}) = 0.45$ and $|\Delta\bar{m}^2_{32}| = 2.51 \times 10^{-3}$ eV$^2$ with 68% confidence intervals of 0.38 - 0.64 and 2.26 - 2.80 $\times 10^{-3}$ eV$^2$ respectively. These results are in agreement with existing antineutrino parameter measurements and also with the $\nu_\mu$ disappearance parameters measured by T2K.

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T2K collaboration, K. Abe, C. Andreopoulos, M. Antonova, S. Aoki, A. Ariga, S. Assylbekov, D. Autiero, M. Barbi, G. J. Barker, G. Barr, P. Bartet-Friburg, M. Batkiewicz, F. Bay, V. Berardi, S. Berkman, S. Bhadra, A. Blondel, S. Bolognesi, S. Bordoni, S. B. Boyd, D. Brailsford, A. Bravar, C. Bronner, M. Buizza Avanzini, R. G. Calland, S. Cao, J. Caravaca Rodríguez, S. L. Cartwright, R. Castillo, M. G. Catanesi, A. Cervera, D. Cherdack, N. Chikuma, G. Christodoulou, A. Clifton, J. Coleman, G. Collazuol, L. Cremonesi, A. Dabrowska, G. De Rosa, T. Dealtry, P. F. Denner, S. R. Dennis, C. Densham, D. Dewhurst, F. Di Lodovico, S. Di Luise, S. Dolan, O. Drapier, K. E. Duffy, J. Dumarchez, S. Dytman, M. Dziewiecki, S. Emery-Schrenk, A. Ereditato, T. Feusels, A. J. Finch, G. A. Fiorentini, M. Friend, Y. Fujii, D. Fukuda, Y. Fukuda, A. P. Furmanski, V. Galymov, A. Garcia, S. G. Giffin, C. Giganti, F. Gizzarelli, M. Gonin, N. Grant, D. R. Hadley, L. Haegel, M. D. Haigh, P. Hamilton, D. Hansen, T. Hara, M. Hartz, T. Hasegawa, N. C. Hastings, T. Hayashino, Y. Hayato, R. L. Helmer, M. Hierholzer, A. Hillairet, A. Himmel, T. Hiraki, S. Hirota, M. Hogan, J. Holeczek, S. Horikawa, F. Hosomi, K. Huang, A. K. Ichikawa, K. Ieki, M. Ikeda, J. Imber, J. Insler, R. A. Intonti, T. J. Irvine. 2015-12-08. Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam. https://doi.org/10.1103/physrevlett.116.181801

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