A comprehensive study of analyzing powers in the proton-deuteron break-up channel at 135 MeV

TL;DR

This study measures analyzing powers in the proton-deuteron break-up at 135 MeV, comparing experimental data with theoretical models to explore three-nucleon force effects and identify discrepancies in polarization predictions.

Contribution

It provides comprehensive experimental data on analyzing powers across various kinematic configurations at 135 MeV, highlighting sensitivities to three-nucleon forces and discrepancies with existing theoretical models.

Findings

Discrepancies observed between data and Faddeev calculations at small azimuthal angles.

Results show significant sensitivity to three-nucleon force effects.

Experimental data covers a wide range of kinematic geometries.

Abstract

A measurement of the analyzing powers for the $^2$H$(\vec{p},pp)n$ break-up reaction was carried out at KVI exploiting a polarized-proton beam at an energy of 135 MeV. The scattering angles and energies of the final-state protons were measured using the Big Instrument for Nuclear-polarization Analysis (BINA) with a nearly $4\pi$ geometrical acceptance. In this work, we analyzed a large number of kinematical geometries including forward-forward configurations in which both the final-state particles scatter to small polar angles and backward-forward configurations in which one of the final-state particles scatters to large polar angles. The results are compared with Faddeev calculations based on modern nucleon-nucleon (NN) and three-nucleon (3N) potentials. Discrepancies between polarization data and theoretical predictions are observed for configurations corresponding to small relative azimuthal angles between the two final-state protons. These configurations show a large sensitivity to 3N force effects.