Search for CP violation in Neutrino and Antineutrino Oscillations by the
T2K experiment with $2.2\times10^{21}$ protons on target
Authors:
K Abe, R Akutsu, A Ali, J Amey, C Andreopoulos, L Anthony, M Antonova, S Aoki, A Ariga, Y Ashida, Y Azuma, S Ban, M Barbi, GJ Barker, GILES Barr, C Barry, M Batkiewicz, F Bench, V Berardi, S Berkman, RM Berner, L Berns, S Bhadra, S Bienstock, A Blondel, S Bolognesi, B Bourguille, SB Boyd, D Brailsford, A Bravar, C Bronner, MB Avanzini, J Calcutt, T Campbell, S Cao, SL Cartwright, A Cervera, A Chappell, C Checchia, D Cherdack, N Chikuma, G Christodoulou, J Coleman, G Collazuol, D Coplowe, A Cudd, A Dabrowska, GD Rosa, T Dealtry
Abstract:
The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of $14.7(7.6)\times 10^{20}$ protons on target in neutrino (antineutrino) mode, 89 $\nu_e$ candidates and 7 anti-$\nu_e$ candidates were observed while 67.5 and 9.0 are expected for $\delta_{CP}=0$ and normal mass ordering. The obtained $2\sigma$ confidence interval for the $CP$ violating phase, $\delta_{CP}$, does not include the $CP$-conserving cases ($\delta_{CP}=0,\pi$). The best-fit values of other parameters are $\sin^2\theta_{23} = 0.526^{+0.032}_{-0.036}$ and $\Delta m^2_{32}=2.463\pm0.065\times10^{-3} \mathrm{eV}^2/c^4$.
