Can Van Hove singularities be observed in relativistic heavy-ion   collisions ?
  Based on general arguments the in-medium quark propagator in a quark-gluon plasma leads to a quark dispersion relation consisting of two branches, of which one exhibits a minimum at some finite momentum. This results in a vanishing group velocity for collective quark modes. Important quantities such as the production rate of low mass lepton pairs and mesonic correlators depend inversely on this group velocity. Therefore these quantities, which follow from self energy diagrams containing a quark loop, are strongly affected by Van Hove singularities (peaks and gaps). If these sharp structures could be observed in relativistic heavy-ion collisions it would reveal the physical picture of the QGP as a gas of quasiparticles. 
Munshi G. Mustafa (Saha Inst. of Nucl. Phys., Kolkata, India) and   Markus H. Thoma (Max-Planck-Institut fuer Extraterrestri...