The Irvine-Michigan-Brookhaven Nucleon Decay Search: Status Report on an Experiment Sensitive to A Lifetime of 10³³ Years

Abstract

We have studied the properties of, and the expected backgrounds in, a totally active 10,000 ton water Čerenkov 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.

The members of the collaboration are the following: M. Goldhaber, Brookhaven National Laboratory B. Cortez, G. Foster, L. Sulak, Harvard University and University of Michigan C. Bratton, W. Kropp, J. Learned, F. Reines, J. Schultz, D. Smith, H. Sobel, C. Wuest, University of California at Irvine J. LoSecco, E. Shumard, D. Sinclair, J. Stone and J. Vander Velde, University of Michigan

Supported in part by the U.S. Department of Energy