Quasi-deuteron effects at intermediate energies

Abstract

It has been shown that photon and pion reactions in certain energy regions are dominated by the absorption on correlated (n-p)-pairs. Therefore, calculations based on quasi-deuteron models describe rather well the present experimental results. However, with more accurate data out of the reactions (γ,np),(γ,N), (π,NN) and (π,N) performed so that the complete kinematics is known, the correlation function of nucleon pairs in nuclei can be studied a quantity very important for our understanding of the nuclear many body system. The dominance for absorption on pairs in reactions with a rather big mismatch in energy and momentum in the entrance channel compared with the exit channel of the reaction asks to take a close look at other reactions wether these effects show up too: in his contribution Laget has shown that with the inclusion of a quasi-deuteron contribution he can explain the enhanced cross section in (e,e')-reactions between the quasifree peak and the Δ-resonance region. Also pick up reactions, above a critical momentum transfer, are dominated by pair correlation effects.

To learn more about single particle wavefunctions, correlation functions and the validity of the impulse approximation, mostly used in the analyses of the data, a combined effort experimentally as well as theoretically has to be undertaken. Thereby, the use of different projectiles as probes in nuclear reactions will help to disentangle and to check the various ingredients entering in a calculation.