Sensitivity of two-fragment correlation functions to initial-state momentum correlations

Two-fragment reduced-velocity correlation functions were measured for small-impact-parameter collisions of ${}^{86}{\mathrm{Kr}\mathrm{}+}^{93}\mathrm{Nb}$ at $E/A=50 \mathrm{MeV}$ and compared to results of many-body Coulomb-trajectory calculations performed for instantaneous and sequential multifragment breakup scenarios. The correlation functions indicate emission on a very short time scale and appear consistent with an instantaneous breakup scenario, even though they exhibit a pronounced dependence on fragment kinetic energy when fragments are emitted at large transverse momenta. For the case of instantaneous breakup, sensitivities to initial-state momentum correlations due to total momentum conservation and to different emission patterns are investigated. For fragments emitted with large transverse momenta, momentum conservation constraints can cause a dependence of reduced-velocity correlation functions on fragment energy and fragment charge similar to those observed experimentally.