Probing the Repulsive Core of the Nucleon-Nucleon Interaction Via the 4He(e, E`pN) Triple-Coincidence Reaction
Author | : |
Publisher | : |
Total Pages | : |
Release | : 2014 |
ISBN-10 | : OCLC:925448028 |
ISBN-13 | : |
Rating | : 4/5 (28 Downloads) |
Book excerpt: We studied simultaneously the 4He(e, e'p), 4He(e, e'pp), and 4He(e, e'pn) reactions at Q2=2 [GeV/c]2 and xB>1, for a (e, e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail of the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.