Search for CP violation in Neutrino and Antineutrino Oscillations by the T2K experiment with $2.2\times 10^{21}$ protons on target

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 $\hat{I}{½}_e$ candidates and 7 anti-$\hat{I}{½}_e$ candidates were observed while 67.5 and 9.0 are expected for $\hat{I}{´}_{CP}=0$ and normal mass ordering. The obtained $2\ddot{I}ƒ$ confidence interval for the $CP$ violating phase, $\hat{I}{´}_{CP}$, does not include the $CP$-conserving cases ($\hat{I}{´}_{CP}=0,\ddot{I}€$). The best-fit values of other parameters are ${\sin }^2\hat{I}{¸}_{23}=0.526_{-0.036}^{+0.032}$ and $\hat{I}”m_{32}^2=2.463_{-0.070}^{+0.071}\times 10^{-3}{\mathrm{eV}}^2/c^4$.

9 pages, 6 figures