The B-10((p)over-right-arrow, gamma)C-11 reaction at astrophysically relevant energies

The B-10(, gamma)C-11 reaction was studied by detecting the gamma-rays produced when 100, 130-, and 160-keV polarized protons were stopped in a thick B-10 target. Polarized and unpolarized incident beams were used to measure the cross section and vector analyzing power as a function of angle and energy for capture to the ground (J(pi)=3/2(-)), the second (E=4319 keV, J(pi)=5/2(-)), and the fifth (E=6478 keV, J(pi)=7/2(-)) excited states of C-11. The data were analyzed to obtain the amplitudes and phases of the contributing transition-matrix elements at each measured energy for all three transitions. Values of the astrophysical S factors were obtained from the cross section data and are compared to previous results. A direct capture plus resonance model calculation was performed in an attempt to account for all measured quantities. It was found that the large (similar to32%) value of A(y)(90degrees) observed in the case of capture to the ground state could be accounted for by including the subthreshold resonance at 8420 keV.