Abstract :
The decoherence induced in the quantum dynamics of a particle by its interaction with the excitations of a metallic wire is studied. We obtain that, even in a ballistic model for the particle, quantum effects at zero temperature are strongly suppressed at length scales longer than lnch, where l is the elastic mean free path in the wire, and nch is the number of electronic channels. A generalization to particles at finite energies gives the same estimate for electrons diffusing at a finite energy. The inclusion of the effects due to the low energy acoustic plasmons modify significantly the scale at which quantum effects are suppressed.