Coherent Compton scattering on light nuclei in the Δ-resonance region

Coherent Compton scattering on light nuclei in the Δ-resonance region is studied in the impulse approximation and is shown to be a sensitive probe of the in-medium properties of the Δ resonance. The elementary amplitude on a single nucleon is calculated from the unitary K-matrix approach developed previously. Modifications of the properties of the Δ resonance due to the nuclear medium are accounted for through the self-energy operator of the Δ, calculated from the one-pion loop. The dominant medium effects such as the Pauli blocking, mean-field modification of the nucleon and Δ masses, and particle-hole excitations in the pion propagator are consistently included in nuclear matter.