When a star undergoes a type II supernova explosion, more than 99% of its gravitational binding energy is released as neutrinos. This results in more neutrinos being produced in the span of a few seconds than are released in the rest of the star's life combined. The neutrinos are predicted to be evenly distributed among the 3 flavours and to have approximately equal numbers of particles and antiparticles. The neutrino flux is so large, in fact, that even a supernova at galactic distances should produce a large number of events in SNO+. Indeed, neutrinos from supernova 1987A, which occurred about 50kpc away from earth in the Large Magellanic Cloud, were detected by the KamiokandeII, IMB and Baksan neutrino detectors (11, 8, and 5 events, respectively in ~13s). This data has been used for everything from testing neutrino oscillation models [1] , to setting limits on neutrino mass [2] , to constraining the size of possible compact dimensions in the universe [3] . In fact, there is a paper [4] entitled "Yet Another Paper on Sn1987a....". If neutrinos from a supernova within our galaxy are ever detected, the greater number of observed events would give much more information about stellar and neutrino physics.


As a large volume scintillator experiment, SNO+ would be a very good supernova detector. The reactions that could be used by SNO+ to detect supernova neutrinos are listed in Table 1, below, along with the number of interactions of each type expected from a 3x1053 erg supernova 10kpc from earth. These different detection channels would give SNO+ some ability to distinguish between νe,νe, νμ,τ and νμ,τ, which is important for many of the physics measurements. A measurement by SNO+ of the neutrino flux from a galactic supernova (if we were lucky enough to have one go off while we were running) would yield extremely useful information about neutrino physics, stellar physics, cosmology, and more.




















                          Table 1: Expected number of neutrino events in the different

                          interaction channels in SNO+ for a 10kpc supernova, assuming

                          MSW oscillations. (**assuming a 0.2MeV threshold).





[1] Lunardini, C., and Smirnov, A. Yu. Astropart. Phys. 21 703 (2004).

[2] Kernan, P.J., and Krauss, L.M., Nucl. Phys. B 437 243 (1995).

[3] Hanhart, C. et al, Phys. Lett. B 509 1 (2001).

[4] Kernan, P.J., and Krauss, L.M., Nucl. Phys. B 437 243 (1995).

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