  The photon analyzing power for the photodisintegration of the deuteron was
measured for seven gamma-ray energies between 2.39 and 4.05 MeV using the
linearly polarized gamma-ray beam of the High-Intensity Gamma-ray Source at the
Duke Free-Electron Laser Laboratory. The data provide a stringent test of
theoretical calculations for the inverse reaction, the neutron-proton radiative
capture reaction at energies important for Big-Bang Nucleosynthesis. Our data
are in excellent agreement with potential model and effective field theory
calculations. Therefore, the uncertainty in the baryon density obtained from
Big-Bang Nucleosynthesis can be reduced at least by 20%.
