Abstract
Observations were made 1570 mwe underground with an 8000 metric ton water Cherenkov detector. During a live-time of 80 days no events consistent with the decay p → e+π° were found in a fiducial mass of 3300 metric tons. We conclude that the limit on the lifetime for bound plus free protons divided by the e+π° branching ratio is τ/B > 1.9 × 1031 yr. (90% confidence). Observed cosmic ray muons and neutrinos are compatible with expectations.
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References and Footnotes
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More precisely, the trigger requires that either 12 PMT’s fire within 50 nsec. or that 3 PMT’s fire in any 2 of 32 groupings of 8 x 8 PMT’s in 150 nsec.
The actual fiducial volume cut is topology dependent and can be as close as 1.0 m from the tube planes in rare cases. This work is supported in part by the U.S. Department of Energy. Our nominal “fiducial mass” is obtained by determining the fraction of simulated events generated throughout the entire detector which pass all of our filtering cuts.
In the energy range with which we are concerned, the ratio is expected to be ~ 2/1. Due to the different sensitivities of our detector to electrons and muons, with the requirement of 45 PMT’s we expect that the observed ratio will be - 0.5.
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Bionta, R.M. et al. (1985). A Search for Proton Decay into e+π° Irvine-Michigan-Brookhaven Collaboration. In: Mintz, S.L., Perlmutter, A. (eds) High-Energy Physics. Studies in the Natural Sciences, vol 20. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-8848-7_3
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DOI: https://doi.org/10.1007/978-1-4684-8848-7_3
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