Testing Dynamical Reduction Models at the Gran Sasso underground laboratory.

The linear and unitary nature of the Schrödinger equation allows the superposition of macro-object states. The wave packet reduction principle avoids superpositions, but its stochastic nature contrasts the deterministic time evolution; the scale of the superposition breakdown is not predicted. Dynamical Reduction Models (DRMs) introduce non-linear and stochastic modifications in the Shrödinger equation, which induce a diffusion process for the state vector, collapsing the wave packet. Charged particles interacting with the stochastic field emit radiation. The results of dedicated measurements will be presented with a setup based on high purity Germanium detectors delivering the most stringent limits on the DRM parameters.