# Investigation of the quasi-free domain in deuteron-deuteron break-up using spin observables

## TL;DR

This study measures spin observables in deuteron-deuteron break-up near the quasi-free regime, revealing the influence of final-state interactions and comparing experimental data with theoretical predictions.

## Contribution

It provides new high-precision measurements of analyzing powers in deuteron break-up at 65 MeV/nucleon, highlighting the role of final-state interactions near the quasi-free domain.

## Key findings

- Data agree with theory at low neutron momenta and high momentum transfer.
- Disagreement increases with neutron momentum, indicating complex interactions.
- Final-state interactions are significant even at small neutron momenta.

## Abstract

Precision measurements of vector and tensor analyzing powers of the $^{2}{\rm H}(\vec d,dp){n}$ break-up process for configurations in the vicinity of the quasi-free scattering regime with the neutron as spectator, are presented. These measurements are performed with a polarized deuteron-beam with an energy of 65 MeV/nucleon impinging on a liquid-deuterium target. The experiment was conducted at the AGOR facility at KVI using the BINA 4$\pi$-detection system. Events for which the final-state deuteron and proton are coplanar have been analyzed and the data have been sorted for various momenta of the missing neutron. In the limit of vanishing neutron momentum and at large deuteron-proton momentum transfer, the data agree well with the measured and theoretically predicted spin observables of the elastic deuteron-proton scattering process. The agreement deteriorates rapidly with increasing neutron momentum and/or decreasing momentum transfer from the deuteron beam to the outgoing proton. This study reveals the presence of a significant contribution of final-state interactions even at very small neutron momenta.