The First K2K event at Super-Kamiokande:
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Artificial Neutrino Beam Detected After Passing Through 250km of Earth
Announced on Monday, June 28, 1999, 14:00 Japan Standard Time
(in USA, = 7 pm Sunday 6/27 Hawaii Standard Time, 10 pm Sunday 6/27 PDT, 1 am Monday 6/28 EDT)
/English/Japanese/
On June 19, 1999, 6:42 PM, Japanese Standard Time, the K2K (KEK to Kamioka) Long Baseline Neutrino Oscillation Experiment observed its first neutrino event due to the KEK neutrino beam in the Super-Kamiokande detector, the first step towards the verification of the neutrino oscillation results announced by the Super-Kamiokande experiment in June last year. This is also the first demonstration that a particle that had been produced artificially and traversed 250km in Earth was detected. The event characteristics are consistent with a neutrino interaction in water. The time of the event is within approximately one micro-second of the expected event time. Both the direction and the time of the event are in the range of expectation considering the detection resolution of the experiment. The probability that the event came from an atmospheric neutrino interaction is estimated to be 0.01%, or one part in ten thousand.
The First K2K event at Super-Kamiokande:
Each PMT's color indicates the time of arrival of the light collected, and the size indicates the amount of charge. The crosses give the reconstructed neutrino interaction vertex, and the diamond marks the neutrino beam direction from the vertex. The right-upper figure is the outer anti detector(OD), which surrounds the inner detector. No response in the OD indicates the interaction occured inside of the inner detector.
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