The scintillation and ionization yield of liquid xenon for nuclear recoils

XENON10 is an experiment designed to directly detect particle dark matter. It is a dual phase (liquid/gas) xenon time-projection chamber with 3D position imaging. Particle interactions generate a primary scintillation signal ( S 1 ) and ionization signal ( S 2 ), which are both functions of the deposited recoil energy and the incident particle type. We present a new precision measurement of the relative scintillation yield L eff and the absolute ionization yield Q y , for nuclear recoils in xenon. A dark matter particle is expected to deposit energy by scattering from a xenon nucleus. Knowledge of L eff is therefore crucial for establishing the energy threshold of the experiment; this in turn determines the sensitivity to particle dark matter. Our L eff measurement is in agreement with recent theoretical predictions above 15 keV nuclear recoil energy, and the energy threshold of the measurement is ∼ 4 keV . A knowledge of the ionization yield Q y is necessary to establish the trigger threshold of the experiment. The ionization yield Q y is measured in two ways, both in agreement with previous measurements and with a factor of 10 lower energy threshold.