Stopped Δ-matter source in heavy-ion collisions at 10 GeV/nucleon?

We predict the formation of highly dense baryon-rich resonance matter in Au+Au collisions at the Brookhaven Alternating Gradient Synchrotron (AGS) energies. The final pion yields show observable signs for resonance matter. The ${\mathrm{\Delta }}_{1232}$ resonance is predicted to be the dominant source for pions of small transverse momenta. Rescattering effects—consecutive excitation and deexcitation of Δ’s—lead to a long apparent lifetime (>10 fm/c) and rather large volumina (several 100 ${\mathrm{fm}}^3$) of the Δ-matter state. Heavier baryon resonances prove to be crucial for reaction dynamics and particle production at AGS.