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Publisher Summary This chapter reviews the N–P Final State Interaction (FSI) angular distribution in deuteron breakup at 45 MeV. An experiment described in the chapter was performed to provide an FSI angular distribution at energy higher than previously available. The experiment was performed with the NRL Sector Focusing Cyclotron using standard coincidence electronics for kinematically complete experiments. The chapter presents a comparison of the data with the results of calculations using several S-wave separable potentials tailored to test for sensitivity to off-shell and on-shell effects. These potentials have been described previously. The potentials have two different form factors A and B: A has off-shell behavior similar to that of the Reid soft core potential while B has off-shell behavior resembling the softer Yamaguchi. The potentials fit two different sets of phase shifts: set 1 corresponds nearly to experimental p–p 90° cross sections and set 2 corresponds to cross sections less than the p–p experimental values at energies above 10 MeV. The results, when put in the context of previous experiments and calculations, emphasize that there are still some basic factors not being considered in deuteron breakup calculations.

Publisher Summary This chapter examines the double spectator process in the 3He(3He,dd)pp reaction. Measurements of nuclear systems with three or four particles in the final state can be influenced by a number of processes: (1) quasifree scattering (QFS), (2) quasifree reactions (QFR), (3) final state interactions (FSI), (4) simultaneous breakup, which results in phase space distribution of events, and (5) second-order effects. The chapter describes an investigation on the four-body continuum for the reaction 3He(3He,dd)pp with two detector-telescopes in coincidence to determine whether the double quasifree scattering (DQFS) process is observable. The 3He(2H,dd)p and 2H(3He,dd)p reactions were also measured for DQFS-equivalent d–d center of momentum conditions with proton spectators in the target and projectile, respectively. The results obtained suggest that the DQFS process is observable, and the comparison of the data to PWIA predictions indicate that 3He has a reasonably strong p + d cluster configuration and that a PWIA analysis is as appropriate for DQFS processes as it is for QFS processes.

Publisher Summary This chapter explores a few nucleon reactions for mass fields greater than three. The majority of these experiments are being done to investigate quasi-free (QF) processes with all possible pairs being observed, including both QF scattering and QF reactions. An important question being addressed is to what extent distorted waves improve the impulse approximation predictions. In few cases, substantial improvements are obtained using distorted waves, but in the tightly bound alpha particle, evidence that plain waves are as appropriate as distorted waves exists. An experimental situation that can cause problems is the spectral structure as a result of 4He excited states. This can cause severe problems with n–n scattering-length experiments, and the success or failure of these experiments can depend upon preselecting the most advantageous regions of phase space. Also, Coulomb FSI occurs in few of these experiments, and this FSI can produce dramatic reductions in the observed cross sections. This effect occurs when two charged particles have almost zero relative energy and no threshold resonance structure. The Coulomb repulsion can dominate, causing a striking dip in the cross section and can interfere with the investigation of other processes.

This chapter discusses quasi-free processes in the 2 H+ 3 He reactions. In the interaction between 3 He and 2 H, there are several three-particle breakup combinations possible. Kinematically, complete measurements were obtained with 2 H beam energies of 22.3 and 35 MeV and 3 He beam energies of 30.0, 33·4, and 52.5 MeV. Charged particle pairs were detected with conditions favoring the observation of quasi-free processes, both quasi-free scattering (QFS) and quasi-free reactions (QFR). The d + d, p + d, and 3 He + p QFS interactions and the 3 He + n→ p + t, d + d → p + t, and 3 He + n → d + d QFR interactions were observed. The chapter presents the analysis of data for a given interaction and comparison of a plane-wave-impulse-approximation prediction. The momentum wave function is extracted for small values of spectator momentum. Data were acquired primarily with a gas cell target having either 2 H or 3 He gas and fixed detector-aperture geometry. The results indicate that there is little difference in d 3 σ (exper)/d 3 σ (PWIA) as a function of beam energy (incoming channel CM energy), and this ratio does not depend on whether the spectator is in the projectile or in the target.

This chapter discusses quasi-free processes in the reaction 3 He + 3 He for E 3He = 50, 65 and 78 MeV. There are several three-particle breakup combinations that can occur when 3 He bombards 3 He. Measurements for a number of quasifree scattering (QFS) and quasifree reactions (QFR) interactions for 3 He + 3 He have been obtained in kinematically complete experiments. Charged particle pairs are detected and conditions are chosen favoring the observation of quasifree processes. The data are analyzed in terms of the plane-wave-impulse-approximation with the Hulthen wave function. In a study described in the chapter, gas cell target and fixed detector-aperture geometry was used. The effective target thickness and detector solid angles were calculated. The calculations were compared to measurements of the product of these parameters from 2 H(p,p) 2 H and 2 H(p,pp)n two- and three-body reactions for E =22 MeV where the d 2 σ and d 3 σ are well known.

Publisher Summary This chapter describes that in a coplanar, kinematically complete experiment, the evidence for a strong p–d final state Coulomb interaction (FSCl) was observed with the 2 H(α, dt) 1 H reaction. Identified particle and coincidence energy information for d and t with various angle pairs was obtained. Such an experiment has the distinct advantages of determining the kinematics of the final state and of distinguishing the final state interaction of interest from other interactions and sequential or quasi-free scattering processes. These advantages have made the application of the Watson–Migdal formalism and other appropriate formulations quite successful in predicting the shape of the spectral structure. In this particular experiment, comparison of theoretical predictions to the data is constrained by the low counting rates encountered and the presence of spectral structure. Though the chapter does not explain the three-body final state cross section for multiparticle breakup experiments with sequential and FSI processes, it explains the factors that contribute to the cross section. The presence of sequence and the insensitivity of the fitting to the effective range parameters limit the interpretation of the p–d FSI. The fits generated suggest that no 3 He excited state exists near its p–d breakup threshold.