Testing the solar neutrino conversion with atmospheric neutrinos

Neutrino oscillations with parameters Delta m.(2) = (2-20) X 10(-5) eV(2), sin(2)2 theta. > 0.65, relevant for large mixing MSW solution of the solar neutrino problem can lead to an observable (up to 10-12%) excess of the e-like events in the sub-GeV atmospheric neutrino sample. The excess has a weak zenith angle dependence in the low energy part of the sample and strong zenith angle dependence in the high energy parr. The excess rapidly decreases with energy of neutrinos, it is suppressed in the multi-GeV sample. These signatures allow one to disentangle the effect of oscillations due to solar Delta m(2) from other possible explanations of the excess. The up-down asymmetry of the excess may change the sign with energy being positive in the sub-GeV region and negative in the multi-GeV range. Predicted properties of the excess are in agreement with the SuperKamiokande data. (C) 1999 Published by Elsevier Science B.V. All rights reserved.