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Stopping upward muon eventsThe smallest atmospheric neutrino dataset is the stopping upward-going muon sample - these are tracks which enter, but do not leave, Super-Kamiokande. As for through-going upward muons, these are produced outside the detector volume and virtually all the result of muon-neutrino interactions, however the neutrinos producing these data carry much less energy than the throughgoing data, Also, they are even more rare. The predicted rate is somewhat greater than 1/3 that of through-going upward muons, however the observed rate is closer to 1/4 (and the observed rate of through-going events is itself lower than expected). The depletion of the stopping muon sample hence gives additional evidence of a disappearance of muon neutrinos, at a rate which is dependent on the neutrino energy. The available data is not yet sufficient to allow a meaningful test of any possible angular dependence, however. |
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