Joint Particle Physics/Nuclear Physics Seminar

The forces between nucleons are one of the most studied problems in physics. With the three-nucleon system being (apart from a few remaining discrepancies such as the Ay puzzle of dp elastic scattering) well described by state-of the-art Faddeev calculations, and with some progress in Faddeev-Yakubovsky calculations, the interest in the four-nucleon system has grown appreciably in recent years. Like the three-nucleon system it is a suitable testing ground for modern meson-exchange nucleon-nucleon forces introduced into these calculations, as well as for the effects of three-(and four-)nucleon forces. Recent successes in ab-initio calculations of levels of light nuclei assign a special role to the four-nucleon scattering system as intermediate between the two-and three-nucleon system and heavier light nuclei.


The use of polarized beams and targets allows to reveal much more information in reactions. Experimental studies of reactions with polarized protons and deuterons at low energies, which have been performed at tandem Van de Graaff accelerator laboratories in Cologne and at TUNL, will be presented. Progress in a better understanding of the 4N system has been made, but open questions remain.