Longitudinal momentum distributions of the reaction residues following fast two-nucleon knockout reactions

Abstract

The longitudinal momentum distributions of the cross sections of heavy projectile-like residues after fast, direct two-like-nucleon knockout reactions are discussed. Both the two-nucleon inelastic breakup (stripping) and the stripping-diffraction removal events are considered. We show that, because the two mechanisms have a very similar nuclear surface localization, they generate essentially identical longitudinal momentum distributions. The approach used combines reaction dynamics, using the sudden, eikonal and spectator-core approximations, with structure wave functions from the many-body shell model. The sensitivities of the resulting longitudinal momentum distributions to the orbital angular momenta, the separation energies, and the angular momentum coupling of the two removed nucleons are clarified. In particular, the widths of these distributions are shown to provide a very clear signal of the total angular momentum of the removed-nucleon pair-pairs coupled to larger total angular momentum giving broader distributions. These now complete distributions, from correlated wave functions, are significantly different from earlier uncorrelated estimates. Confirmation of these theoretical expectations is presented, based on very recent intermediate-energy, residue final-state inclusive and exclusive two-nucleon removal measurements.

Correlations probed in direct two-nucleon removal reactions

“…For the spin J i = 0 + projectile nucleus examples used in Ref. [11], there was a high sensitivity of the residue momentum distributions to the final-state total angular momentum J f = I . Moreover, the shapes of these calculated distributions were robust with respect to variations of other key structure and reaction parameters, such as the nucleon separation energy.…”

In-beamγ-ray spectroscopy ofMg35and

“…1. Since the measurement's main focus was the study of 36 Mg in the two-proton knockout from 38 Si [13,27,28], the magnetic rigidity of the S800 spectrograph was set to center the longitudinal momentum distribution of 36 Mg 9 Be( 38 Si, A Z)X at 83 MeV/u mid-target energy. All reaction residues can be unambiguously identified by plotting the energy loss measured in the S800 ionization chamber versus the ion's time of flight.…”

Triple configuration coexistence inS44

“…[24,25] and extended in [26,27], demonstrates that the reaction dynamics restrict direct two-nucleon removal events to grazing collisions. In this way the collision samples the joint position and momentum configurations of the two removed nucleons [28].…”