The Irvine-Michigan-Brookhaven Nucleon Decay Facility: Status Report on a Proton Decay Experiment Sensitive to a Lifetime of 1033 Years and a Long Baseline Neutrino Oscillation Experiment Sensitive to Mass Differences of Hundredths of an Electron Volt
We have studied the properties of, and the expected backgrounds in, a totally active 10,000 ton water Cerenkov detector located deep underground and sensitive to many of the conjectured decay modes of the nucleons in it. Identification of (π, μ) and (e, γ) secondaries, good energy resolution, and good angular resolution provide sufficient background rejection in the detector under construction to permit one to obtain significant information about several decay channels, should they be observed. If no events were recorded in the device in one year, a lower limit of ~1033 years would be placed on the partial lifetime for the most distinct nucleon decay modes. Depending upon the decay channel, this is ~3 orders of magnitude longer than previous measurements, and is at or beyond the level suggested by many unifying theories. The sensitivity predicted for this instrument is within an order of magnitude of that achievable in an arbitrarily large detector of this general type, since known background from atmospheric neutrinos imposes an inherent limit.
We also detail the capabilities of a search for neutrino oscillations sensitive to low energy atmospheric ve’s and vμ’s using as a baseline the diameter of the earth. A flux independent asymmetry in the up/down ratio of the two neutrino species is the primary signal. The full 10,000 water Cerenkov detector is necessary; smaller detectors would have insufficient statistical power. For a two year exposure, the detector provides a several standard deviations signal for maximal mixing of either species over the mass difference range of 10-3 to 10-1 eV. The upper end of this range coincides with the lower end of conceivable accelerator-based searches for neutrino oscillations.
KeywordsNeutrino Oscillation Charged Lepton Atmospheric Neutrino Neutrino Flux Fermi Motion
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