Scintillation efficiency and ionization yield of liquid xenon for monoenergetic nuclear recoils down to 4 keV

Liquid xenon (LXe) is an excellent material for experiments designed to detect dark matter in the form of weakly interacting massive particles (WIMPs). A low energy detection threshold is essential for a sensitive WIMP search. The understanding of the relative scintillation efficiency (Leff) and ionization yield of low energy nuclear recoils in LXe is limited for energies below 10 keV. In this article, we present new measurements that extend the energy down to 4 keV, finding that Leff decreases with decreasing energy. We also measure the quenching of scintillation efficiency caused by the electric field in LXe, finding no significant field dependence.