Photo-disintegration of $^3$He below E$_\gamma$ = 15 MeV at HI$\vec{\gamma}$S

Differential cross sections of the $^3$He($\gamma$,n)pp reaction have been measured at HI$\vec{\gamma}$S. Measurements were taken at E$_{\gamma}$ = 11.4, 12.8, 13.5, and 14.7 MeV. The breakup neutrons were detected using liquid scintillator detectors placed at 75 cm from the target center and at the scattering angles of $\theta$ = 50$^{\circ}$, 75$^{\circ}$, 90$^{\circ}$, 105$^{\circ}$, 130$^{\circ}$, and 160$^{\circ}$. At a given scattering angle, theory\footnote{Deltuva {\it et.~al.~} Phys. Rev. \textbf{C72} 054004 (2005)} predicts that $\frac{d^3\sigma}{dE_n d\Omega_n}(E_n)$ peaks near $E_n^{max}$. This peaking in the energy distribution is predicted to begin around E$_{\gamma}$ = 10 MeV and becomes more pronounced as the incident $\gamma$-ray energy is increased. Below E$_{\gamma}$ = 10 MeV and at a given scattering angle the predicted neutron energy distribution is consistent with a {\it phase space only} neutron energy distribution. The measured differential cross sections for E$_{\gamma}$ = 11.4 and 12.8 MeV do not show peaking in the neutron energy distribution as predicted by theory, and the shape of the energy distribution at a given scattering angle is consistent with the shape of a phase space distribution. The peaking near $E_n^{max}$ of the energy distribution is observed at E$_{\gamma}$ = 13.5 and 14.7 MeV.