OMNIS - AN IMPROVED LOW-COST DETECTOR TO MEASURE MASS AND MIXING OF MU TAU NEUTRINOS FROM A GALACTIC SUPERNOVA/

OMNIS is an observatory for multiflavour interactions from Galactic su pernovae. It has evolved from the Supernova Neutrino Burst Observatory (SNBO) proposed by Cline et al., based on the detection of the neutri nos by neutral current nuclear excitation in natural rock. This would result in the emission of neutrons, which could be captured by counter s embedded in the rock. This scheme would be sensitive principally to the higher temperature mu and tau neutrinos and would allow time-of-fl ight measurement of neutrino mass if in the cosmologically interesting range 10-100 eV. The present paper proposes a new neutron detection a rrangement which improves detection efficiency and reduces cost by a f actor similar to 30, allowing the time profile of over 2000 nu(mu tau) events to be recorded with only 200 tons scintillator. This new schem e represents the optimum configuration for a natural underground rock target. A Galactic supernova signal would be a factor 10-30 above neut ron background (from cosmic ray muons and alpha activity) in sites wit h depth > 500 mwe. Another major improvement results by supplementing the rock with more favourable target elements such as iron or lead, gi ving sensitivity to all three neutrino types and mixing between these. Some calculations are included on the speculative possibility of extr a-Galactic supernova neutrino detection using this principle. (C) 1997 Elsevier Science B.V.