Through-going muons
Fully-Contained Partially-Contained Through-going muons Stopping muons Solar Neutrinos

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Through-going upward muon events

Neutrinos interact not only with the water in our detector, but also with the rock surrounding it. Both electron- and muon-neutrino interactions in the nearby rock create charged particles, but any electrons produced outside Super-Kamiokande are absorbed before travelling even a meter, By contrast, muons are able to travel a considerable distance. Muons which arrive from above the detector cannot be separated from the more mundane cosmic-ray muons, but those which arrive from below (upward-going muons) are almost all the result of neutrino interactions.

The rate of such events is much less than for contained events, however by only considering muons which travel a substantial distance in the detector volume, and then exit, we arrive at a dataset which is primarily produced by high energy neutrinos.

Hence the overall rate of these muon-neutrino products can be measured, as well as the number arriving from the side and from directly below. We find an overall depletion which is consistent with that for contained events, but both the theoretical and experimental uncertainties are larger here than in the latter case. In addition, there is evidence for an angular dependence of the depletion which is again consistent with the Multi-GeV data, but not yet significant on its own.

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Dave Casper