Experimental study of upward-going muons in Kamiokande.

Abstract

Upward-going muons produced in the surrounding rock by high-energy neutrinos from astronomical objects have been searched for using the large underground water Cherenkov detector, Kamiokande. During a total of 1255 days observation, no significant signal was observed from the direction of eight astronomical objects. The 90%-confidence-level (-C.L.) upper limits on upward-going muon fluxes with energy greater than 1.7 GeV are 9.9×10−14 cm−2s−1 for Cygnus X-3 and 2.6×10−14 cm−2s−1 for LMC X-4. Our observed upward-going muon flux is compared with the calculation of the upward-going muon flux produced by the atmospheric neutrinos to examine the neutrino-oscillation hypothesis. The experimental average upward-going muon flux with energy greater than 1.7 GeV, (2.05±0.18)×10−13 cm−2s−1sr−1, is consistent with the theoretical expectation. If νμ⇆ντ vacuum oscillations and large mixing angle are assumed, Δm2≳10−2 eV2 is newly rejected. The 90%-C.L. upper limit on the Δm2 for the maximum mixing is found to be Δm2=0.03 eV2 and Δm2=0.0055 eV2, depending on assumptions.Received 29 September 1988DOI:https://doi.org/10.1103/PhysRevD.39.1481©1989 American Physical Society