Effects of exchange, final-state interactions, and distorted waves in the reactions 2H( 3He, 3H p)p and 2H( 3He, 3He p)n

Abstract

A systematic treatment of the 2H( 3He 3H p)p and 2H( 3He, 3He p)n reactions by the Born approximation is carried out for conditions at which Warner et al. (WBDFF) observed spectator peaks juxtaposed with final-state interaction (FSI) effects. WBDFF fitted the spectator peaks with plane-wave Born approximation (PWBA) using two interaction matrix elements, but encountered difficulties in predicting relative yields, absolute cross sections and the shape modifications due to FSI. We first add full antisymmetry to PWBA in order to account properly for relative yields. This step connects all reaction mechanisms (break-up, knock-out, and pick-up), and their seven distinct interaction matrix elements. Next, the FSI shape modifications are successfully accounted for by using scattering wave functions for the final free nucleons in one of the matrix elements and by inferring the FSI properties in all matrix elements through a scattering-length approximation. When juxtaposed to simple spectator poles the FSI effects are shown to be interesting interference dips and amplitude peaks which are dominated by the sign and size of the singlet and triplet nueleon-nucleon scattering lengths. Finally, the effects of distorted waves on absolute cross sections are briefly discussed.