Graduate student Georgios Laskaris recently published a paper in Physical Review Letter titled "First measurements of spin-dependent double-differential cross sections and the Gerasimov-Drell-Hearn integrand from 3He(g,n)pp at incident photon energies of 12.8 and 14.7 MeV" under the supervision of his advisor Prof. Haiyan Gao together with the Capture Group at TUNL, other collaborators from Duke and elsewhere, and several theory collaborators from Europe. This is the first paper in PRL on the topic of spin-dependent breakup cross sections of 3He and the Gerasimov-Drell-Hearn (GDH) sum rule integrand below pion production threshold. The GDH sum rule relates dynamic quantities as the spin-depedent photo-disintegration cross sections to the anomalous magnetic moment of a nucleon or nucleus.
The experiment took place at the HIgS facility of TUNL. A 3He target polarized using the spin-exchange optical pumping technique and a circularly polarized gamma-ray beam were employed. The neutrons coming from the three-body break up of 3He were detected using 16 liquid scintillator detectors. The results were compared with the state-of-the-arts three body calculations and clearly favor the theory which includes the Coulomb interaction. This shows that the inclusion of Coulomb repulsion in the theoretical calculations is of utmost importance for this particular process. Further, the extracted GDH integrand values establish the first steps towards the investigation of GDH sum rule below pion production threshold.