We use trajectory calculations to analyze small-angle particle-particle correlations for three typical situations: ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au (E/A=60 MeV)${\to }^2$H${\mathrm{-}}^2$H pairs and ${}_{}{}^1{}_{}{}^{}\mathrm{-}_{}^1{}_{}{}^{}$H pairs, ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$${+}^{59}$Cu (E/A=30 MeV)→n-n pairs. For the ${}_{}{}^2{}_{}{}^{}\mathrm{-}_{}^2{}_{}{}^{}$H pairs our analysis of the gentle featureless anticorrelations suggests that the major driving force is Coulomb repulsion after a range of average time delays from ≊5×${10}^{\mathrm{-}21}$ s for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ pairs of lower energy to ≊${10}^{\mathrm{-}22}$ s for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ pairs of higher energy. Simulations are used to illustrate the separate dominance of source size and lifetime in the space-time extent of the emitter. For lifetimes ≤${10}^{\mathrm{-}22}$ s the emitter size dominates; for longer lifetimes the time delays become predominant. The peaks at ≊20 MeV/c in the correlation functions for ${}_{}{}^1{}_{}{}^{}\mathrm{-}_{}^1{}_{}{}^{}$H pairs can be accounted for by diproton ejection which decays into protons with a Q value of ≊0.35 MeV and a decay width of ≊1 MeV (or a meanlife of 6×${10}^{\mathrm{-}22}$ s). The positive correlations between neutron pairs can be accounted for by dineutron ejection which decays into neutrons with a near zero Q value and a decay width of ≊0.25 MeV (or a meanlife of ≊2×${10}^{\mathrm{-}21}$ s). If these diproton and dineutron clusters do indeed have a metastable existence, then one should reexamine the notion that their associated small-angle correlations reflect the space-time extent of the emission source.

• Received 24 May 1993

DOI:https://doi.org/10.1103/PhysRevC.48.2874