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

Coherent Compton scattering on light nuclei in the ∆ resonance region is studied in the impulse approximation and is shown to be a sensitive probe of the in-medium properties of the ∆ resonance. The elementary amplitude on a single nucleon is calculated from the unitary K-matrix approach developed previously. Modifications of the properties of the ∆ resonance due to the nuclear medium are accounted for through the self-energy operator of the ∆, calculated from the one-pion loop. The dominant medium effects such as the Pauli blocking, mean-field modification of the nucleon and ∆ masses, and particle-hole excitations in the pion propagator are consistently included in nuclear matter. 2001 PACS numbers: 25.20.Dc, 13.60.Fz