Gravity wave and neutrino bursts from stellar collapse: A sensitive test of neutrino masses

New methods are proposed with the goal to determine absolute neutrino masses from the simultaneous observation of the bursts of neutrinos and gravitational waves emitted during a stellar collapse. It is shown that the neutronization electron neutrino flash and the maximum amplitude of the gravitational wave signal are tightly synchronized with the bounce occurring at the end of the core collapse on a time scale better than 1 ms. The existing underground neutrino detectors (SuperKamiokande, SNO,...) and the gravity wave antennas soon to operate (LIGO, VIRGO,...) are well matched in their performance for detecting galactic supernovae and for making use of the proposed approach. Several methods are described, which apply to the different scenarios depending on neutrino mixing. Given the present knowledge on neutrino oscillations, the methods proposed are sensitive to a mass range where neutrinos would essentially be mass degenerate. The 95% C.L. upper limit which can be achieved varies from 0.75 eV/c2 for large νe survival probabilities to 1.1 eV/c2 when in practice all νe's convert into νμ's or ντ's. The sensitivity is nearly independent of the supernova distance