Search for Nucleon Decay: The Deep Underground Water Cerenkov Detector and the Homestake Tracking Spectrometer
We report the initial result of a search for nucleon decay using a 300-ton water Cerenkov detector located 1480 m underground in the Homestake gold mine at Lead, South Dakota. We find TN > 2.4 × 1031 B μ y, where TN is the nucleon total lifetime and where B μ is the model-dependent probability of production and detection of a stopping and decaying muon following a nucleon decay event. In the SU(5) grand unified model, calculations of B μ vary from approximately 5 to 10%, thereby yielding nucleon total lifetime limits ranging from 1 to 2 × 1030 y.
We also describe our plans for a conceptually new nucleon decay detector which will permit study of this process for lifetimes up to 3 × 1032 y. This detector will be a completely-vetoed completely-active 1000-ton liquid scintillation tracking spectrometer also located at a depth of 1480 m in the Homestake Gold Mine. This instrument will be sensitive to all nucleon decay modes; it will have a spatial resolution of 30 cm (0.6 radiation lengths), thereby permitting identification of the decay secondaries; it will measure the total ionization energy released by the nucleon decay with a resolution of 10%, thereby permitting study of the inclusive decay mode distribution by observing the full energy peak and neutrino escape peaks; and it will measure the charge of lepton secondaries as well as the polarization of secondary muons. By virtue of its excellent energy and spatial resolution and great depth underground, the spectrometer will be remarkably free of background and ambiguity.
KeywordsExpense Calorimeter Cali Hine
Unable to display preview. Download preview PDF.
Footnotes and References
- 3.For an excellent and thorough review of grand unification and nucleon decay, see P. Langacker, SLAC-PUB-2544, to be published in Physics Reports.Google Scholar
- 6.R.I. Steinberg and J.C. Evans, Jr., Proc. Int. Conf. on Neutrino Physics and Neutrino Astrophysics, Baksan Valley (Acad. of Sciences of the USSR, Moscow, 1978), p. 321.Google Scholar
- 7.E. Fireman, ibid., p. 53.Google Scholar
- 8.The thickness of this detector (12.5 cm) was much less than the expected range of nucleon decay products (typically about 1 m). Because of this limitation, most of the nucleon decays which this instrument would have detected would have taken place in the rock surrounding the detector. Much of the nucleon decay information would therefore have been lost, in contrast to the situation with the present 120 cm-thick Homestake detector.Google Scholar
- 11.Preliminary results of this experiment have been reported previously by M. Deakyne et al., Proc. XVth Rencontre de Moriond, March 1980; Proc. First Workshop on Grand Unification, Durham, N.H., April 1980.Google Scholar
- 12.M. Deakyne, W. Frati, K. Lande, C.K. Lee, R.I. Steinberg, and E. Fenyves, Proc. Neutrino’78, West Lafayette, April 1978; Proc. Conf. on Nucleon Stability, Madison, Dec. 1978.Google Scholar
- 13b.Bulg. J. Phys. 5, 433 (1978)).Google Scholar
- 15.G.L. Cassiday, J.W. Keuffel, and J.A. Thompson, Phys. Rev. D7, 2022 (1973).Google Scholar
- 16.S. Miyake, Proc. 13th Int. Conf. on Cosmic Rays, Denver, 1973, p. 3638.Google Scholar
- 17.G. Kane and G. Karl, Phys. Rev. D22, 2808 (1980).Google Scholar
- 18.J.F. Donoghue, Phys. Lett. 92B, 99 (1980).Google Scholar
- 19.E. Golowich, Phys. Rev. D22, 1148 (1980).Google Scholar