Δ's in nuclei

Δ-excitations as studied by charge-exchange reactions are discussed. Spectra from (3He, t), (d, 2p[1S0]) and charge-exchange reactions with heavy ions like (12C, 12N) and (16O, 16N) are shown. In all these reactions the Δ-excitation is seen as a prominent part of the spectra. In all the reactions a shift is observed between the energy of the Δ-peak in nuclei (A ⩾ 12) and on the proton. Also discussed is the quasi-elastic peak seen in the (3He, t) and (d, 2p[1S0]) reactions. We follow the peak from q ∼ 1.3 to 2.5 fm−1 and see a shift of the centroid energy relative to the free nucleon as a function of q.