The free stochastic limit of interacting quantum fields

The problem of obtaining the quantum stochastic limit for a system interact ing with a reservoir is investigated when both are considered as quantum fi elds. The pre-limit fields are as encountered in standard quantum field the ory and in particular we do not resort to the simplifying responseless inte raction for the reservoir field. In the separation of time scales between t he unperturbed (slow) and interaction (fast) dynamics we find a new quantum stochastic noise emerging which describes multi-particle scatterings and h as extended free statistics. We give explicit diagrammatic rules to compute the an-point correlators of the noise.