ar X iv : a st ro - p h / 97 05 19 7 v 1 2 4 M ay 1 99 7 UNDERGROUND MUONS IN SUPER - KAMIOKANDE

The largest underground neutrino observatory, Super-Kamiokande, located near Kamioka, Japan has been collecting data since April 1996. It is located at a depth of roughly 2.7 kmwe in a zinc mine under a mountain, and has an effective area for detecting entering-stopping and through-going muons of about 1238 m 2 for muons of > 1.7 GeV. These events are collected at a rate of 1.5 per day from the lower hemisphere of arrival directions, with 2.5 muons per second in the downgoing direction. Fig. 1: The effective area for muons versus zenith angle in Super-Kamiokande. The filled region is for muons with more than 1.7 GeV of energy upon entering the inner detector, including those that stop in the detector. The upper curve shows the mean pathlength in the detector for throughgoing muons. We report preliminary results from 229 live days analyzed so far with respect to zenith angle variation of the upcoming muons. These results do not yet have enough statistical weight to discriminate between the favored hypothesis for muon neutrino oscillations and no-oscillations. We report on the search for astrophysical sources of neutrinos and high energy neutrino fluxes from the sun and earth center, as might arise from WIMP annihilations. None are found. We also present a topographical map of the overburden made from the downgoing muons. The detector is performing well, and with several years of data we should be able to make significant progress in this area. THE NEUTRINO DETECTOR The Super-Kamiokande detector, located in a mine tunnel in Western Japan, has been accumulating data for more than one year now, having begun recording data on 1 April 1996. The detector is described elsewhere (Conner, 1997 in these proceedings , and references therein). Herein we focus upon the preliminary results obtained upon upcom-ing and sidegoing muons produced by cosmic ray muon neutrino (and anti-neutrino) interactions in the rock surrounding the detector. Simply, one can picture the instrument as a 36.2 m tall by 33.8 m diameter cylindrical Cherenkov inner detector with surrounding veto counter. DATA SAMPLE AND REDUCTION Data is recorded at about 12 event triggers per second, depending upon the low energy threshold setting (typically around 5.5 MeV). The downgoing cosmic ray muons account for about 2.5/sec, and constitute the bulk of the recorded data, which total nearly 25 GBytes/day. Solar neutrinos and contained neutrino interactions occur at the rate of about 19/day and 9/day, …