Probing nuclear properties beyond the mean field

Abstract

Three experimental activities related to the question of short-range correlations (SRCs) in nuclei are reported. The shell-model occupancy of 3s protons in 208Pb has been determined by the CERES method to be (77 ± 9)%. The depletion exceeds that predicted from long-range correlations alone, but is weaker than predicted from some models accounting for SRCs. More direct evidence for SRCs is expected from (γ, 2 N ) experiments with 100 ≲ E γ ≤ 500 MeV performed at MAMI-B. As a very promising first result we are able to present 6Li(γ,pn) cross sections whose energy dependence for transitions from the 1p and 1s shells, respectively, differ remarkably. Finally, in studying pionic double-charge-exchange reactions which are known to depend on nucleon-nucleon correlations in nuclei, we discovered a candidate for a narrow πNN resonance called d′ with I( J P ) = 0(0 −) at 2.06 GeV. The various experiments persued in the hunt for this dibaryon state are described.