Two-deuteron radiative capture: Polarization observables at Ed

Abstract

Measurements of the $^{2}\mathrm{H}$(d\ensuremath{\rightarrow},\ensuremath{\gamma}${)}^{4}$He cross section \ensuremath{\sigma}(\ensuremath{\theta}), the vector analyzing power ${\mathit{A}}_{\mathit{y}}$(\ensuremath{\theta}), and the tensor analyzing power ${\mathit{A}}_{\mathit{y}\mathit{y}}$(\ensuremath{\theta}) have been obtained at ${\mathit{E}}_{\mathit{d}}$(lab)=14.7 and 1.2 MeV and ${\mathit{E}}_{\mathit{d}}$(lab)\ensuremath{\le}0.8 MeV; the spherical tensor analyzing power ${\mathit{T}}_{20}$(\ensuremath{\theta}) was also measured at ${\mathit{E}}_{\mathit{d}}$(lab)=14.7 MeV. ${\mathit{A}}_{\mathit{y}}$(130\ifmmode^\circ\else\textdegree\fi{}) and ${\mathit{A}}_{\mathit{y}\mathit{y}}$(130\ifmmode^\circ\else\textdegree\fi{}) were measured at eight bombarding energies between ${\mathit{E}}_{\mathit{d}}$(lab)=0.8 and 14.7 MeV and ${\mathit{T}}_{20}$(130\ifmmode^\circ\else\textdegree\fi{}) at ten energies between ${\mathit{E}}_{\mathit{d}}$(lab)=5.4 and 14.7 MeV. A transition-matrix element analysis is performed by fitting to the available angular distribution data at ${\mathit{E}}_{\mathit{d}}$(lab)\ensuremath{\le}0.8 MeV and at ${\mathit{E}}_{\mathit{d}}$(lab)=1.2 and 14.7 MeV. The data are compared to the results of a multichannel resonating group model (MCRGM) calculation. The MCRGM model includes the tensor force in calculating both the continuum and bound states and provides a fairly good description of the data, especially above ${\mathit{E}}_{\mathit{d}}$=5 MeV. This calculation predicts a D-state probability in $^{4}\mathrm{He}$ arising from the relative motion between the two deuterons of ${\mathit{P}}_{\mathit{D}}$=2.2%.