Liquid xenon and argon, dark matter detectors with background rejection

The potential of liquids xenon and argon as dark matter targets is discussed emphasizing the former. Significant discrimination of very small signals against beta / gamma backgrounds can be achieved in several ways; firstly via the collection of scintillation light alone in conjunction with a likelihood technique to fully exploit the digitized photon arrival times; secondly via the collection of both light and ionisation charge, either in a simple ionisation chamber or in the proportional scintillation mode. Published alpha and beta data are used to assess the discrimination