Three-flavor MSW solutions of the solar neutrino problem - art. no. 013002

We perform an updated phenomenological analysis of the Mikheyev-Smirnov-Wol fenstein (MSW) solutions of the solar neutrino problem, assuming oscillatio ns between two and three neutrino families. The analysis includes the total rates of the Homestake. SAGE, GALLEX, Kamiokande and Super-Kamiokande expe riments, as well as the day-night asymmetry and the 18-bin energy spectrum of Super-Kamiokande. Solutions are found at several values of the theta(13) mixing angle. Among the most interesting features, we find that solar neut rino data alone put the constraint theta(13)less than or similar to 55 degr ees-59 degrees at 95% C.L., and that a fraction of the MSW solutions extend s at and beyond maximal (nu(1), nu(2)) mixing (theta(12)greater than or equ al to pi/4), especially if the neutrino square mass splitting is in its low er range (m(2)(2)- m(1)(2)similar to 10(-7) eV(2)) and if theta(13) is nonz ero. In particular, bimaximal (or nearly bimaximal) mixing is possible for atmospheric and MSW solar neutrino oscillations within the stringent reacto r bounds on theta(13).