Discrimination of nuclear recoils from alpha particles with superheated   liquids
  The PICASSO collaboration observed for the first time a significant difference between the acoustic signals induced by neutrons and alpha particles in a detector based on superheated liquids. This new discovery offers the possibility of improved background suppression and could be especially useful for dark matter experiments. This new effect may be attributed to the formation of multiple bubbles on alpha tracks, compared to single nucleations created by neutron induced recoils. 
F. Aubin, M. Auger, E. Behnke, B. Beltran, K. Clark, X. Dai, A.   Davour, M.-H. Genest, G. Giroux, R. Gornea, R. Faust, C.B....