  We introduce an abstract class of bosonic QFT Hamiltonians and study their
spectral and scattering theories. These Hamiltonians are of the form
$H=\d\G(\omega)+ V$ acting on the bosonic Fock space $\G(\ch)$, where $\omega$
is a massive one-particle Hamiltonian acting on $\ch$ and $V$ is a Wick
polynomial $\Wick(w)$ for a kernel $w$ satisfying some decay properties at
infinity. We describe the essential spectrum of $H$, prove a Mourre estimate
outside a set of thresholds and prove the existence of asymptotic fields. Our
main result is the {\em asymptotic completeness} of the scattering theory,
which means that the CCR representations given by the asymptotic fields are of
Fock type, with the asymptotic vacua equal to the bound states of $H$. As a
consequence $H$ is unitarily equivalent to a collection of second quantized
Hamiltonians.
