  Relations between photon scattering, entanglement and multi-mode detection
are investigated. We first establish a general framework in which one- and
two-photon elastic scattering processes can be discussed, then we focus on the
study of the intrinsic entanglement degradation caused by a multi-mode
detection. We show that any multi-mode scattered state cannot maximally violate
the Bell-CHSH inequality because of the momentum spread. The results presented
here have general validity and can be applied to both deterministic and random
scattering processes.
