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تسجيل مستخدم جديدThe likelihood for supernova neutrino analyses
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We derive the event-by-event likelihood that allows to extract the complete information contained in the energy, time and direction of supernova neutrinos, and specify it in the case of SN1987A data. We resolve discrepancies in the previous literature, numerically relevant already in the concrete case of SN1987A data.
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We examine active-sterile neutrino conversion in the late time post-core-bounce supernova environment. By including the effect of feedback on the Mikheyev-Smirnov-Wolfenstein (MSW) conversion potential, we obtain a large range of neutrino mixing para
meters which produce a favorable environment for the r-process. We look at the signature of this effect in the current generation of neutrino detectors now coming on line. We also investigate the impact of the neutrino-neutrino forward scattering-induced potential on the MSW conversion.
Core-collapse supernovae emit of order $10^{58}$ neutrinos and antineutrinos of all flavors over several seconds, with average energies of 10--25 MeV. In the Sudbury Neutrino Observatory (SNO), a future Galactic supernova at a distance of 10 kpc woul
d cause several hundred events. The $ u_mu$ and $ u_tau$ neutrinos and antineutrinos are of particular interest, as a test of the supernova mechanism. In addition, it is possible to measure or limit their masses by their delay (determined from neutral-current events) relative to the $bar{ u}_e$ neutrinos (determined from charged-current events). Numerical results are presented for such a future supernova as seen in SNO. Under reasonable assumptions, and in the presence of the expected counting statistics, a $ u_mu$ or $ u_tau$ mass down to about 30 eV can be simply and robustly determined. This seems to be the best technique for direct measurement of these masses.
Supernovae are rare nearby, but they are not rare in the Universe, and all past core-collapse supernovae contributed to the Diffuse Supernova Neutrino Background (DSNB), for which the near-term detection prospects are very good. The Super-Kamiokande
limit on the DSNB electron {it antineutrino} flux, $phi(E_ u > 19.3 {rm MeV}) < 1.2$ cm$^{-2}$ s$^{-1}$, is just above the range of recent theoretical predictions based on the measured star formation rate history. We show that the Sudbury Neutrino Observatory should be able to test the corresponding DSNB electron {it neutrino} flux with a sensitivity as low as $phi(22.5 < E_ u < 32.5 {rm MeV}) simeq 6 $ cm$^{-2}$ s$^{-1}$, improving the existing Mont Blanc limit by about three orders of magnitude. While conventional supernova models predict comparable electron neutrino and antineutrino fluxes, it is often considered that the first (and forward-directed) SN 1987A event in the Kamiokande-II detector should be attributed to electron-neutrino scattering with an electron, which would require a substantially enhanced electron neutrino flux. We show that with the required enhancements in either the burst or thermal phase $ u_e$ fluxes, the DSNB electron neutrino flux would generally be detectable in the Sudbury Neutrino Observatory. A direct experimental test could then resolve one of the enduring mysteries of SN 1987A: whether the first Kamiokande-II event reveals a serious misunderstanding of supernova physics, or was simply an unlikely statistical fluctuation. Thus the electron neutrino sensitivity of the Sudbury Neutrino Observatory is an important complement to the electron antineutrino sensitivity of Super-Kamiokande in the quest to understand the DSNB.
Various statistical issues relevant to searches for new physics or to parameter determination in analyses of data in neutrino experiments are briefly discussed.
Scalar (fermion) dark matter with mass in the MeV range coupled to ordinary neutrinos and another fermion (scalar) is motivated by scenarios that establish a link between radiatively generated neutrino masses and the dark matter relic density. With s
uch a coupling, cosmic supernova neutrinos, on their way to us, could resonantly interact with the background dark matter particles, giving rise to a dip in their redshift-integrated spectra. Current and future neutrino detectors, such as Super-Kamiokande, LENA and Hyper-Kamiokande, could be able to detect this distortion.
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