Search for GUT monopoles at Super-Kamiokande

GUT monopoles captured by the Sun's gravitation are expected to catalyze proton decays via the Callan-Rubakov process. In this scenario, protons, which initially decay into pions, will ultimately produce v(e), v(mu) and (v) over bar (mu) After undergoing neutrino oscillation, all neutrino species appear when they arrive at the Earth, and can be detected by a 50.000 metric ton Water Cherenkov detector, Super-Kamiokande (SK). A search for low energy neutrinos in the electron total energy range from 19 to 55 MeV was carried out with SK and gives a monopole flux limit of F-M(sigma(0)/1 mb) < 6.3 x 10(-24)(beta(M)/10(-3))(2) cm(-2) s(-1) sr(-1) at 90% C.L., where beta(M) is the monopole velocity in units of the speed of light and sigma(0) is the catalysis cross section at beta(M) = 1. The obtained limit is several orders of magnitude more stringent than the current best cosmic-ray super-massive monopole flux limit for beta(M) < 10(-2) and also two orders of magnitude lower than the result of the Kamiokande experiment, which used a similar detection method. (C) 2012 Elsevier B.V. All rights reserved.