Collision statistics in a dilute granular gas fluidized by vibrations in   low gravity
  We report an experimental study of a dilute "gas" of inelastically colliding particles excited by vibrations in low gravity. We show that recording the collision frequency together with the impulses on a wall of the container gives access to several quantities of interest. We observe that the mean collision frequency does not scale linearly with the number N of particles in the container. This is due to the dissipative nature of the collisions and is also directly related to the non extensive behaviour of the kinetic energy (the granular temperature is not intensive). 
Eric Falcon (Phys-ENS), S. Auma\^itre (LPS), P. Evesque (LMSSM), F.   Palencia (ICMCB), C. Lecoutre-Chabot (ICMCB), S. Fauve...