Session Q10 - Few-Body Systems in Nuclear Physics.
INVITED session, Monday afternoon, May 01
104C, LBCC
A series of bremsstrahlung measurements have been performed at KVI with the new superconducting cyclotron, AGOR, aiming to investigate the behavior of the nucleon-nucleon interaction beyond what is already known from the elastic N\!N interaction and the properties of the deuteron. Nucleon-nucleon bremsstrahlung is the simplest process used for such studies as it involves the strong interaction between two nucleons and the well-known electromagnetic interaction. \par Recently, the study of the nucleon-nucleon interaction by means of the bremsstrahlung process below the particle-production threshold has been receiving increasing attention both theoretically and experimentally. The reason for this is the success of modern potential-model calculations on the one hand and the advent of high-precision detection systems covering a large part of the phase space on the other. Polarized beams have also delivered a boost to the experimental efforts. In the past decade, several groups have been working on the new generation measurements, the results of which are now emerging. \par At KVI, we have used the high-quality polarized beam of 190 MeV protons to perform the most complete experiment to date on proton-proton and proton-deuteron systems. The second system was chosen so that one is able to study all possible bremsstrahlung channels, including the neutron-proton system. High precision cross-section and analyzing-power data have been obtained for the real-photon production on these systems enabling one to extract information on the properties of the interacting nucleon as it propagates in an intermediate state, the role of virtual nucleon-resonance excitation at lower energies and the role of two-body effects such as MEC. Simultaneously, we have measured the lepton pair production on both systems. This latter process, despite its lower cross section, avails us with extra degrees of freedom, namely the non-zero invariant mass and the outgoing lepton angles making the study of other structure functions than the transverse one possible. Experimental results of the real and virtual photon production on both systems, along with the results of theoretical calculations will be discussed.