Microscopic background calculations for (p, n) reactions at intermediate energies

The background of ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(p, n)$ and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}(p, n)$ spectra has been calculated in a microscopic model for an incident proton energy of 160 MeV. The continuous parts of the spectra are reproduced within a factor of 1.3. It is shown that most of the background subtracted in the experimental analysis of the ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}(p, n)$-Gamow-Teller resonance is actually Gamow-Teller strength. The calculations predict a strong $\Delta L=2\mathrm{}$ ($3^{+}$) resonance in ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}(p, n)$ at 25 MeV excitation energy, but none in ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$.