Spin-isospin selectivity in three-nucleon forces

Precision data are presented for the break-up reaction, (2)H((p) over right arrow, pp)n, within the framework of nuclear-force studies. The experiment was carried out at KVI using a polarized-proton beam of 190 MeV impinging on a liquid-deuterium target and by exploiting the detector, BINA. Some of the vector-analyzing powers are presented and compared with state-of-the-art Faddeev calculations including three-nucleon forces effect. Significant discrepancies between the data and theoretical predictions were observed for kinematical configurations which correspond to the (2)H((p) over right arrow,(2)He)n channel. These results are compared to the (2)H((p) over right arrow, d)p reaction to test the isospin sensitivity of the present three-nucleon force models. The current modeling of two and three-nucleon forces is not sufficient to describe consistently polarization data for both isospin states. (C) 2010 Elsevier B.V. All rights reserved

Cross-section and analyzing-power measurements in three and four-nucleon scattering

The physics phenomena of nuclei are for a large part understood by considering the interaction between two of its building elements, the nucleons. In the past, the existence of an additional force, the three-nucleon (3N) interaction, was proven rigorously by a comparison between precision data and state-of-the-art calculations. The exact magnitude and the structure of this 3N force is still poorly understood and more experimental studies are needed. We successfully studied a few scattering reactions at intermediate energies at KVI using a unique and advanced detection system called BINA. This facility enabled us to perform cross sections and polarization measurements with an excellent statistical and systematical precision. The rst reaction which was studied is the proton-deuteron elastic scattering process. The results of this experiment resolved an important discrepancy which was found in the past between two published datasets taken at KVI and at RIKEN in Japan. In addition, we evaluated the energy dependence of this channel by systematically analyzing the existing world dataset and the newly measured data with BINA. In the second reaction, we studied the deuteron-deuteron scattering process. The elastic, neutron-transfer, and deuteron break-up channels were identi ed uniquely. This is the rst time that di erential cross sections and polarization observables of the deuteron break-up reaction leading to a three-body nal-state were measured with high precision in a nearly background-free experiment. The obtained dataset for the deuteron-deuteron scattering at intermediate energies will reveal many details of the 3N interaction by a comparison with upcoming theoretical calculations of the four-nucleon scattering system.