SUPERKAMIOKANDE AND SOLAR ANTINEUTRINOS

We propose to exploit the angular distribution of the positrons emitte d in the reaction <(nu)over bar>(e) + p --> n + e(+) to extract a poss ible antineutrino signal from the Superkamiokande background. From the statistics collected in just 101.9 days one obtains a model independe nt upper bound on the antineutrino flux Phi(nu)- (E-nu-> 8.3 MeV) < 9 . 10(4) cm(-2) s(-1) at the 95% C.L. By assuming the same energy spect rum as for the B-8 neutrinos, the 95% C.L. bound is Phi(nu)- (E-nu-> 8 .3 MeV) < 6 . 10(4) cm(-2) s(-1). Within three years of data taking, t he sensitivity to nu(e) --> <(nu)over bar>(e) transition probability w ill reach the 1% level, thus providing a stringent test of hybrid osci llation models. (C) 1997 Elsevier Science B.V.