Implications of the triplet-Majoron model for the supernova SN1987A

We address several possible implications of the triplet-Majoron (TM) model for supernova physics, such as cooling and rapid deleptonization. We find that recent observations of the neutrinos from SN1987A are consistent with the TM model even if the ${\nu }_e$ ${\nu }_e$-Majoron coupling constant is $g_{\mathrm{ee}}$≃0.7×${10}^{\mathrm{-}3}$ suggested by a recent ββ-decay experiment. We find specifically that deleptonization via ${\nu }_e$ ${\nu }_e$→${\chi }^0$, followed by conversion to χ${¯}^0$, is unlikely to be important for this value of $g_{\mathrm{ee}}$; however, if $g_{\mathrm{ee}}$≃$g_{\mu \mu }$≃$g_{\tau \tau }$, neutrino species equilibration via ${\nu }_e$ ${\nu }_e$→${\nu }_{\mu }$ ${\nu }_{\mu }$ and ${\nu }_e$ ${\nu }_e$→${\nu }_{\tau }$ ${\nu }_{\tau }$ is likely to occur on a time scale of ∼${10}^{\mathrm{-}4}$ sec. Rapid equilibration, followed by decay in flight via ${\nu }_{\mu }$(${\nu }_{\tau }$)→ν${¯}_e$+${\chi }^0$, can dramatically enhance the chance of observing neutronization neutrinos, even for $g_{\mu e}^2$ and $g_{\tau e}^2$≃${10}^{\mathrm{-}18}$. This last effect might be detected in nearby supernovas.