Experimental study of upward-going muons in Kamiokande

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^-2{s}^{{{-}}1}for Cygnus X-3 and 2.6×{10}^{{{-}}14}$ ${cm}^{{{-}}2}s^-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^-2{s}^{{{-}}1}sr^-1, is consistent with the theoretical expectation. If ν_μ{}ν_τ vacuum oscillations and large mixing angle are assumed, {Δ}m²{}10^-2 eV² is newly rejected. The 90%-C.L. upper limit on the {Δ}m² for the maximum mixing is found to be {Δ}m²=0.03 eV² and {Δ}m²=0.0055 eV², depending on assumptions.