Large Solar-Flares - Analysis Of The Events Recorded By The Mont-Blanc Neutrino Detector

The results of the analysis of events recorded by the Mont Blanc neutrino detector during the occurrence of 19 large solar flares, in the period 1988 August-1990 March (including the two powerful flares on 1989 September 29 and October 19) are reported and discussed. No significant neutrino signal was found in time coincidence with solar flares.Upper limits (90% C.L.) obtained on the integral neutrino and antineutrino flux of different flavors are F(nu-e approximately) < 1.3 x 10(10)(2.2 x 10(9)) cm-2 [10 (20) < E-nu < 100 MeV], F(nu-e) < 2.3 x 10(10) cm-2(25 < E-nu < 100 MeV), F(nu-mu) < 3.8 x 10(11) cm-2(20 < E-nu < 100 MeV), and F(nu-mu approximately) < 4.0 x 10(11) cm-2(20 < E-nu < 100 MeV). In particular, the nu-e flux is considerably lower than the flux required to explain the excess of nu-e captures observed by the Homestake Cl-37 solar neutrino experiment during runs 19, 27, and 71, when large solar flares occurred.