For Physicists

Observation of νe Appearance (Summer 2013)

The νe appearance analysis was performed on our entire data-set up to April 12th, 2013 (A beam exposure of 6.39×1020 p.o.t.). We observed 28 single-ring electron-like events at Super-Kamiokande while 4.64±0.53 events would be expected if sin2(2θ13) = 0. The probability of background fluctuation resulting in 28 or more events being observed is 9.9×10-14, which, when converted to a significance level, is 7.5σ. The fitted value of sin2(2θ13) is 0.150+0.039-0.034 (0.182+0.046-0.040) assuming δCP = 0, |Δm232| = 2.4×10-3 eV2, θ23 = π/4 and normal (inverted) hierarchy. This is the first ever observation of an explicit νe appearance channel.

Nu_e appearance result in summer 2013

Our results for the normal (left) and inverted (right) hierarchies. The areas between colored lines show allowed regions of sin2(2θ13) for each value of δCP at 68% (green) and 90% (blue) confidence level. The black solid line is the best fit value of sin2(2θ13) for each assumed value of δCP and the mass hierarchy.