One- and two-step contributions to theZr90(p,n)90Nb cross section at0°

Within a multiple collision theory based on the eikonal approximation we study the ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$(p,n${)}^{90}$Nb 0° cross section at 200 MeV incident proton energy. Both the one- and two-step contributions are calculated and compared to the experimental inclusive cross section. Good agreement between theory and experiment is found. Possible implications for the ‘‘missing Gamow-Teller strength’’ are discussed.