Particle production by time-dependent meson fields in relativistic   heavy-ion collisions
  Collective bremsstrahlung of vector meson fields caused by mutual deceleration of the colliding nuclei is considered within the time-dependent Walecka theory. Excitation functions and rapidity distributions of particles produced by this mechanism are calculated under some simplifying assumptions about the space-time variation of the baryon current in a nuclear collision. In the case of central Au+Au collisions the bremsstrahlung mechanism becomes comparable with particle production in incoherent hadron--hadron collisions above the AGS energies. 
I.N. Mishustin, L.M. Satarov, H. Stoecker and W. Greiner