Evaluation of high energy natural neutrino experiments

The directional intensities of neutrinos of various types produced in the decay of cosmic ray secondaries in the earth's atmosphere have been estimated. The calculated energy spectra are believed to be uncertain by <20% for neutrino energies up to 100 GeV. Using these fluxes and making various assumptions about the behaviour of neutrino cross-section with energy, the energy spectra of neutrino-induced muons at large depths underground have been calculated. It is shown that a cross-section increasing only linearly with energy up to ∼ 100 GeV. would account only for about one-fifth of the preliminary counting rate observed in a recent underground experiment. A more rapid increase in cross-section is indicated somewhere between 10 GeV. and 100 GeV. and this is shown to be quantitatively consistent with the existence of a charged intermediate boson of mass 2 GeV. ∼ M_w < 5 GeV. (However see the note added in proof.) The question of detecting high energy neutrino signals from extra-terrestrial sources is briefly discussed.