Probing nucleon-nucleon correlations with (e,e'p) and (e,e'pp) reactions

Abstract

Some of the recent attempts to detect signals of nucleon-nucleon correlations with semi-exclusive A(e,e'p) and exclusive A(e,e'pN) processes are reviewed. Unfactorized and distorted-wave calculations for these processes are discussed. The calculations implement two-body currents stemming from pion-exchange and intermediate $\Delta$ excitation. The two-body currents are shown to be highly competitive with the mechanisms related to nucleon-nucleon correlations. This observation seriously hampers attempts to link semi-exclusive A(e,e'p) measurements, which probe high missing energies, to the correlated part of the nuclear spectral function. Signals of central short-range correlations (SRC) have been detected in (e,e'pp) measurements on ^{12}C and ^{16}O, thereby confirming the picture that in hadronic matter SRC solely affect nucleon pairs with a small center-of-mass momentum and residing in a relative S state.