The ¹⁰B(p⃗,γ)¹¹C reaction at astrophysically relevant energies

The ¹⁰B(p⃗,γ)¹¹C reaction was studied by detecting the γ-rays produced when 100-, 130-, and 160-keV polarized protons were stopped in a thick ¹⁰B 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^π=3∕2⁻), the second (E=4319 keV,J^π=5∕2⁻), and the fifth (E=6478 keV,J^π=7∕2⁻) excited states of ¹¹C. 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 (∼32%) value of A_y(90°) observed in the case of capture to the ground state could be accounted for by including the sub-threshold resonance at 8420 keV.