The Photon Polarization Parameter of ²H(n,γ)³H reaction with Inclusion of the Electric Quadrupole Contribution

We use effective field theory (EFT) for the calculation of neutron–deuteron radiative capture at very low energies. We present here the use of EFT to calculate a low-energy photo-nuclear observable in three-body systems, the photon polarization parameter and fore–aft asymmetry at thermal neutron energies up to next-to-next to leading order (N²LO), with inclusion of the electric quadrupole contribution. The photon polarization parameter in total is found to be R_c=?0.421±0.003 and is in good agreement with the other modern theoretical calculations based on modern nucleon–nucleon potentials. In comparison with our previous work, a satisfactory agreement with the available experimental data is found by inclusion of the electric quadrupole contribution.