Abstract
A quantum many-body model is presented with features similar to those of certain particle detectors. The energy spectrum contains a single, thermodynamically metastable "ready" state and macroscopically-distinct, ground "pointer" states. Transitions into classical-like states can be triggered by a single particle with the help of the thermal bath. Schrödinger cat states are associated with superpositions of inequivalent vacua, thus suggestion a relationship between wave function collapse and the dynamics of symmetry breaking in phase transformations.