Alternatives for understanding qualitative features that dominate particle-particle correlations in heavy-ion reactions of ≊50 MeV/nucleon

We use trajectory calculations to analyze small-angle particle-particle correlations for three typical situations: [sup 40]Ar+[sup 197]Au ([ital E]/[ital A]=60 MeV)[r arrow][sup 2]H-[sup 2]H pairs and [sup 1]H-[sup 1]H pairs, [sup 20]Ne+[sup 59]Cu ([ital E]/[ital A]=30 MeV)[r arrow][ital n]-[ital n] pairs. For the [sup 2]H-[sup 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 [approx]5[times]10[sup [minus]21] s for the [sup 2]H pairs of lower energy to [approx]10[sup [minus]22] s for the [sup 2]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 [le]10[sup [minus]22] s the emitter size dominates; for longer lifetimes the time delays become predominant. The peaks at [approx]20 MeV/[ital c] in the correlation functions for [sup 1]H-[sup 1]H pairs can be accounted for by diproton ejection which decays into protons with a [ital Q] value of [approx]0.35 MeV and a decay width of [approx]1 MeV (or a meanlife of 6[times]10[sup [minus]22] s). The positive correlations between neutron pairs can be accounted for by dineutron ejection which decays into neutrons with a near zero [italmore » Q] value and a decay width of [approx]0.25 MeV (or a meanlife of [approx]2[times]10[sup [minus]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.« less