A study of atmospheric neutrino interactions in the Kamiokande II detector
Neutrinos are produced when cosmic rays collide with nitrogen and oxygen in the atmosphere. They are interesting because they produce background in proton decay experiments and because they might demonstrate that neutrinos are massive, contrary to the Standard Model of Electroweak Interactions. The relative abundance of muon and electron flavor neutrinos in a 2.74 kton-yr sample of neutrino interactions from Kamiokande II was measured with two independent methods. In the first, the fraction of all neutrino candidates accompanied by a muon decay signal was smaller than predicted (2.7$\sigma$). In the second, events were classified as electron flavor neutrino candidates (E class), muon flavor neutrino candidates (M class), and inelastic interaction candidates (X class) without scanning. The distribution of events amongst the classes was self consistent and was consistent with the decay analysis; however, the ratio of M events to E events, divided by the predicted ratio, was 0.44 $\pm$ 0.09(stat) $\pm$ 0.07(syst), when it should have been one. It was concluded that the rate of muon neutrino candidates, relative to the rate of electron neutrino candidates, was less than predicted. These results confirm other independent analyses.
Frank, Edward Davidson, "A study of atmospheric neutrino interactions in the Kamiokande II detector" (1992). Dissertations available from ProQuest. AAI9308569.