Correlations probed in direct two-nucleon removal reactions

TL;DR

This paper investigates how two-nucleon removal reactions can reveal details about the orbital angular momentum and wave functions of nucleon pairs, providing a new way to test nuclear structure models.

Contribution

It clarifies that the total orbital angular momentum L, rather than the total angular momentum I, primarily influences the momentum distribution shapes, enabling model validation.

Findings

Momentum distributions depend strongly on the orbital angular momentum L.

Accurate measurements can assess the accuracy of nuclear wave function models.

Reactions can probe subtle structure aspects of two-nucleon configurations.

Abstract

Final-state-exclusive momentum distributions of fast, forward travelling residual nuclei, following two nucleon removal from fast secondary radioactive beams of projectile nuclei, can and have now been measured. Assuming that the most important reaction mechanism is the sudden direct removal of a pair of nucleons from a set of relatively simple, active shell-model orbital configurations, such distributions were predicted to depend strongly on the total angular momentum I carried by the two nucleons - the final state spin for spin 0+ projectiles. The sensitivity of these now-accessible observables to specific details of the (correlated) two-nucleon wave functions is of importance. We clarify that it is the total orbital angular momentum L of the two nucleons that is the primary factor in determining the shapes and widths of the calculated momentum distributions. It follows that, with accurate measurements, this dependence upon the L make-up of the two-nucleon wave functions could be used to assess the accuracy of (shell- or many-body) model predictions of these two-nucleon configurations. By use of several tailored examples, with specific combinations of active two-nucleon orbitals, we demonstrate that more subtle structure aspects may be observed, allowing such reactions to probe and/or confirm the details of theoretical model wave functions.