Nuclear spallation-fragmentation reactions induced by high-energy projectiles

In a fragmentation or spallation reaction a target nucleus is hit by a high-energy projectile (proton or heavy ion). In the fast step of the reaction highly excited intermediate nuclei, the prefragments, are formed. They decay to the particle stable final fragments in a second step. We treat the first step in Glauber theory. For the decay chain we propose a master equation and solve it by converting it to a differential equation. Analytical solutions are obtained. They clarify the underlying physics: The mass yield curve σ(A) of the final fragments is directly related to the distribution of excitation energy in the prefragments. The isobaric cross sections σ(A,N-Z) for fixed A are dominated by the level density of the final fragment at its lowest particle threshold. Some properties of the target, like its neutron excess, enter via a memory factor. The formulas are successfully compared to the data.NUCLEAR REACTIONS Spallation and fragmentation reactions; projectile protons of several GeV, various targets; theory for cross sections; two step model; fast step Glauber theory; analytical formula for evaporation chains.