A measurement of the efficiency for the detection of neutrons, in the momentum range 200–3200 MeV/c, in large volume liquid scintillation counters

We describe a system of 194 large volume liquid scintillation counters designed to detect neutrons in an experiment on the reaction π − p → π 0 n in the resonance region. The detection efficiency of the system has been determined, as a function of neutron momentum, in three separate measurements, covering the range 200–3200 MeV/c. Below 400 MeV/ c the efficiency shows the expected momentum dependence near threshold, rising to a maximum of 50% near 300 MeV/ c and then falling to 43% near 400 MeV/ c . In the region 400–700 MeV/ c the efficiency rises to 47% near 600 MeV/ c and falls again to 43%, an effect not seen before; the efficiency was expected to be almost momentum independent in this region. Above the threshold for inelastic processes on nucleon-nucleon collisions (∼800 MeV/ c ) the efficiency rises significantly reaching a maximum value of 65% above 1700 MeV/ c .