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arXiv · 1804.04912

Final results of the OPERA experiment on $\nu_\tau$ appearance in the CNGS beam

OPERA Collaboration·N. Agafonova·A. Alexandrov·A. Anokhina·S. Aoki·A. Ariga·T. Ariga·A. Bertolin·C. Bozza·R. Brugnera·A. Buonaura·S. Buontempo·M. Chernyavskiy·A. Chukanov·L. Consiglio·N. D'Ambrosio·G. De Lellis·M. De Serio·P. del Amo Sanchez·A. Di Crescenzo·D. Di Ferdinando·N. Di Marco·S. Dmitrievsky·M. Dracos·D. Duchesneau·S. Dusini·T. Dzhatdoev·J. Ebert·A. Ereditato·J. Favier·R. A. Fini·F. Fornari·T. Fukuda·G. Galati·A. Garfagnini·V. Gentile·J. Goldberg·Y. Gornushkin·S. Gorbunov·G. Grella·A. M. Guler·C. Gustavino·C. Hagner·T. Hara·T. Hayakawa·A. Hollnagel·K. Ishiguro·A. Iuliano·K. Jakovcic·C. Jollet·C. Kamiscioglu·M. Kamiscioglu·S. H. Kim·N. Kitagawa·B. Klicek·K. Kodama·M. Komatsu·U. Kose·I. Kreslo·F. Laudisio·A. Lauria·A. Ljubicic·A. Longhin·P. Loverre·A. Malgin·M. Malenica·G. Mandrioli·T. Matsuo·V. Matveev·N. Mauri·E. Medinaceli·A. Meregaglia·S. Mikado·M. Miyanishi·F. Mizutani·P. Monacelli·M. C. Montesi·K. Morishima·M. T. Muciaccia·N. Naganawa·T. Naka·M. Nakamura·T. Nakano·K. Niwa·N. Okateva·A. Olchevsky·S. Ogawa·K. Ozaki·A. Paoloni·L. Paparella·B. D. Park·L. Pasqualini·A. Pastore·L. Patrizii·H. Pessard·C. Pistillo·D. Podgrudkov·N. Polukhina·M. Pozzato·F. Pupilli
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Abstract

The OPERA experiment was designed to study $\nu_\mu\to\nu_\tau$ oscillations in appearance mode in the CNGS neutrino beam. In this letter we report the final analysis of the full data sample collected between 2008 and 2012, corresponding to $17.97\cdot 10^{19}$ protons on target. Selection criteria looser than in previous analyses have produced ten $\nu_\tau$ candidate events, thus reducing the statistical uncertainty in the measurement of the oscillation parameters and of $\nu_\tau$ properties. A multivariate approach for event identification has been applied to the candidate events and the discovery of $\nu_\tau$ appearance is confirmed with an improved significance level of 6.1 $\sigma$. $\Delta m^2_{23}$ has been measured, in appearance mode, with an accuracy of 20%. The measurement of $\nu_\tau$ CC cross-section, for the first time with a negligible contamination from $\bar{\nu}_\tau$, and the first direct observation of the $\nu_\tau$ lepton number are also reported.

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OPERA Collaboration, N. Agafonova, A. Alexandrov, A. Anokhina, S. Aoki, A. Ariga, T. Ariga, A. Bertolin, C. Bozza, R. Brugnera, A. Buonaura, S. Buontempo, M. Chernyavskiy, A. Chukanov, L. Consiglio, N. D'Ambrosio, G. De Lellis, M. De Serio, P. del Amo Sanchez, A. Di Crescenzo, D. Di Ferdinando, N. Di Marco, S. Dmitrievsky, M. Dracos, D. Duchesneau, S. Dusini, T. Dzhatdoev, J. Ebert, A. Ereditato, J. Favier, R. A. Fini, F. Fornari, T. Fukuda, G. Galati, A. Garfagnini, V. Gentile, J. Goldberg, Y. Gornushkin, S. Gorbunov, G. Grella, A. M. Guler, C. Gustavino, C. Hagner, T. Hara, T. Hayakawa, A. Hollnagel, K. Ishiguro, A. Iuliano, K. Jakovcic, C. Jollet, C. Kamiscioglu, M. Kamiscioglu, S. H. Kim, N. Kitagawa, B. Klicek, K. Kodama, M. Komatsu, U. Kose, I. Kreslo, F. Laudisio, A. Lauria, A. Ljubicic, A. Longhin, P. Loverre, A. Malgin, M. Malenica, G. Mandrioli, T. Matsuo, V. Matveev, N. Mauri, E. Medinaceli, A. Meregaglia, S. Mikado, M. Miyanishi, F. Mizutani, P. Monacelli, M. C. Montesi, K. Morishima, M. T. Muciaccia, N. Naganawa, T. Naka, M. Nakamura, T. Nakano, K. Niwa, N. Okateva, A. Olchevsky, S. Ogawa, K. Ozaki, A. Paoloni, L. Paparella, B. D. Park, L. Pasqualini, A. Pastore, L. Patrizii, H. Pessard, C. Pistillo, D. Podgrudkov, N. Polukhina, M. Pozzato, F. Pupilli. 2018-04-13. Final results of the OPERA experiment on $\nu_\tau$ appearance in the CNGS beam. https://doi.org/10.1103/physrevlett.120.211801

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