Abstract
The first measurements of the three-body phototdisintegration of 3 He polarized parallel and anti-parallel to a circularly polarized γ -ray beam were carried out at the High Intensity γ -ray Source (HIγ S) facility located at Triangle Universities Nuclear Laboratory (TUNL). A high pressure 3 He target, polarized via spin-exchange optical pumping with alkali metals, was used in the experiments. The neutrons from the three-body photodisintegration were detected with sixteen 12.7 cm diameter liquid scintillator detectors. The spin-dependent cross sections and the contributions from the three-body photodisintegration to the 3 He Gerasimov-Drell-Hearn sum rule integrand were extracted and compared with state-of-the-art three-body calculations at the incident photon energies of 12.8, 14.7, and 16.5 MeV. The calculations, which include the Coulomb interaction are in good agreement with the results of the measurements at 12.8 and 14.7 MeV but deviate from the results at 16.5 MeV.
Highlights
Sum rules involving the spin structure of the nucleon and nuclei offer an important opportunity to study QCD
The GDH sum rule relates the energy-weighted difference of the spindependent total photo-absorption cross sections σP and σA to the anomalous magnetic moment of the target nucleus/nucleon as follows: IGDH =
The short-dashed double dotted and the long-dashed curves are the estimations of the GDH integral for the two- and three-body photodisintegration from Deltuva et al Their sum amounts to 142 μb
Summary
The first term can be measured experimentally by carrying out double-polarized two-body and three-body photodisintegration experiments in this energy region and it can be estimated based on the state-of the-art three-body calculations. The state-of-the-art three–body calculations which can estimate the first part of the integral in Eq (2) are performed mainly through the machinery of Faddeev [6] and Alt-Grassberger-Sandhas equations (AGS) [7], and have been carried out for both two-body and three-body photodisintegration of 3He with double polarizations.
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