Evidence for nonequilibrium proton emission in a low-energy heavy-ion reaction

Correlation functions for $p-p,$ $p-d,$ $p-\alpha ,$ $d-\alpha ,$ and $\alpha -\alpha$ were measured for the ${}^{16}\mathrm{O}{+}^{27}\mathrm{Al}$ system at a beam energy of 72 MeV. The detector array was centered at laboratory angle of $20°.$ Compared to published data obtained at larger scattering angles, an unexpected dependence on angle is seen for the $p-p$ channel. The observed anticorrelation is stronger at more forward angles, which suggests that correlation functions are sensitive to the specific reaction mechanisms producing the light-charged particles.