Photonuclear reactions of calcium isotopes calculated with the nuclear shell model

•We calculate photoabsorption cross sections in calcium isotopes.•Large-scale shell-model calculations with the Lanczos method are adopted.•The photoabsorption cross sections in calcium-48 are excellently reproduced.•The existence of a pygmy dipole resonance in calcium-52 is predicted.

Photoabsorption cross sections in calcium isotopes are investigated theoretically with the most advanced nuclear-structure calculations using the nuclear shell model. We show that the photoabsorption cross sections in 48Ca dominated by a giant dipole resonance (GDR) are well reproduced with the shell model and predict that a pygmy dipole resonance (PDR) appears in 52Ca in the low-energy tail of GDR. Excellent agreement with the experiment is achieved due to highly correlated many-body wave functions obtained by treating a huge matrix with the dimension of ∼1010.