First Measurement of the Nuclear-Recoil Ionization Yield in Silicon at 100eV.

Abstract

We measured the nuclear-recoil ionization yield in silicon with a cryogenic phonon-sensitive gram-scale detector. Neutrons from a monoenergetic beam scatter off of the silicon nuclei at angles corresponding to energy depositions from 4keV down to 100eV, the lowest energy probed so far. The results show no sign of an ionization production threshold above 100eV. These results call for further investigation of the ionization yield theory and a comprehensive determination of the detector response function at energies below the keV scale.