Scintillation properties of liquid argon with ion-beam excitation

Liquid rare gases in general and liquid argon in particular are good detector media for the search for rare event physics, like the direct detection of Dark Matter or the search for the neutrinoless double beta decay. However, in this kind of experiments a background suppression on an event-by-event basis is needed. We investigated the scintillation properties of liquid argon both wavelength- and time-resolved with high resolution and best statistics, using different ion beams (protons, sulfur, and gold) as incident particles. The studies showed that particle discrimination using the wavelength information of the scintillation light alone is not feasible. The time information of the scintillation light, particularly the intensity ratio of its fast and slow component, however, provides the desired parameter which can be used for particle discrimination. In this talk the experimental setup used for the studies is presented, and the outcome of the studies is discussed, focussing on the application of LAr in future experiments in astroparticle physics.