A LEAD ASTRONOMICAL NEUTRINO DETECTOR - LAND

The development of a sensitive detector for neutrinos of astronomical origin (simply called astronomical neutrinos hereafter) would make pos sible detailed investigation of supernovae (SN) and open the way for t he discovery of new astronomical phenomena. The neutrino weak interact ion cross section at energies less than 100 MeV increases with Z due t o correlated nucleon effects and the nuclear Coulomb factor (Fermi fun ction). Therefore neutrino detection based on high Z materials will gi ve the largest possible cross sections and best possible neutrino dete ction efficiency. This physics argument motivated us to study lead as a detector of SN. The neutrino cross section for neutron production on lead through the reaction Pb(v(e,mu,tau,) l + n) X is approximate to 10(-40) cm(2), for energies up to 50 MeV, where X refers to Pb, Bi or Tl, the product nuclei of the reactions, e refers to the scattered lep ton, and n refers to neutrons. Neutron production will occur for all t ypes of neutrinos and the neutrons can be detected easily and efficien tly. The detector is uniquely sensitive to all neutrinos but <(nu)over bar (e)>. We show that a SN at the centre of the galaxy produces abou t 1000 neutrons in a 1 kiloton detector. This large number will make i t possible to measure the mass of nu(mu) and nu(tau) neutrinos between 10 and 100 eV with a precision of 10 eV. Further, we describe a possi ble detector in which one also detects the associated electromagnetic energy in coincidence with the neutrons. The coincidence makes this de tector essentially background free. It is possible to expand such a de tector to a size which will reach SN well beyond our galaxy. We calcul ate the nu-Pb cross section, discuss the design, neutrino mass resolut ion, neutron detection efficiency and signal to noise ratio aspects of these detectors.