Reflections on the search for particle dark matter by direct experiments
Since the daring intuition by Fritz Zwicky in 1933 about the existence of dark matter in the Universe, in spite of the extensive investigations pursued over a very long lapse of time, the nature of this matter and of its (other than gravitational, if any) interactions have remained unknown. Very likely, at least a fraction of this matter consists of fossil particles; a possibility that in the last decades has prompted direct and indirect searches for these relics. Particular attention has been (and is being) devoted to the investigation about the physical effects that fossil particles, and in particular Weakly Interacting Particles (WIMPs), moving in our galaxy can produce when they scatter off the material of an appropriate underground detector. In this note we consider the present status of this type of experimental investigation, and comment about some important results obtained recently by the DAMA Collaboration and their possible developments.