Search for atmospheric neutrino oscillations with the Soudan 2 detector

Conference · Mon Jan 20 04:00:00 EST 1992

OSTI ID:10122584

Roback, D M ^[1]

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1. Minnesota Univ., Minneapolis, MN (United States)

Underground proton decay detectors record a sizeable number of atmospheric neutrino-induced events. These neutrinos come primarily from the decay of pions and muons produced in cosmic ray showers in the earth`s atmosphere. The expected flux ratio of muon neutrinos to electron neutrinos traversing an underground detector, {nu}{mu}/{nu}{sub e}, is about 2. The combined effects of detector systematics and nuclear cross section differences between {nu}{sub mu} and {nu}{sub e} interactions typically reduce the measured {nu}{sub mu}/{nu}{sub 3} event ratio to about 1. Over the last decade, both the Kamioka detector in Japan and the IMB detector in the United States have made high-statistics measurements of the atmospheric neutrino event ratio. Both groups have presented strong experimental evidence that the underground {nu}{sub mu}/{nu}{sub e} event ratio is substantially smaller than predicted. In both cases, a statistically significant deficit of muon neutrino-induced events is measured. One possible explanation of the muon neutrino deficit is that these neutrinos are undergoing flavor oscillations between their production points in the atmosphere and their interaction points in underground detectors. An MSW effect interpretation of solar neutrino experiments implies a {nu}{sub e} {yields} {nu}{sub mu} oscillation region in {delta}m{sup 2}-sin{sup 2}(2{theta}) space at least two orders of magnitude lower in {delta}m{sup 2} than the best fit point of the Kamioka result. It is therefore usually assumed that the relevant flavor oscillation for atmospheric muon neutrinos would be {nu}{sub mu} {yields} {nu}{sub r}. The Soudan 2 nucleon decay detector is now approaching completion and collecting data. It will be able to make low-background measurements of atmospheric neutrinos in the next few years to check the possibility that atmospheric neutrinos undergo detectable flavor oscillations.

• Research Organization: Argonne National Lab., IL (United States). High Energy Physics Div.
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 10122584
• Report Number(s): ANL-HEP-CP--92-03; CONF-9111141--3; ON: DE92007397; IN: PDK-498
• Country of Publication: United States
• Language: English

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