A low-temperature proton detector for a neutron lifetime experiment

In this paper the measurement of the neutron lifetime by low-temperature proton detector has always been an active area in fundamental physics. The experimental value, together with one correlation between the products of the neutron beta decay, protons, electrons and antineutrinos, allows to address one of the main problems in the standard model of particle physics, the unitarity of the Cabibbo-Kobayashi-Maskawa matrix. The most promising experimental method is the storage of ultra-cold neutrons (UCN). These very slow neutrons have the pleasant property to be reflected when hitting walls from suitable materials. Hence they may be stored in bottles and the lifetime may be determined by varying the storage time and observing the number of surviving neutrons. Read-out should best be done by LAAPD detectors. Characterization measurements concerning the detection of low-energy protons and the temperature dependence of the scintillation efficiency of Csl as well as the LAAPD sensitivity in the up to now unexplored region down to 20 K had, however, to be performed before a final decision.