Probing chiral dynamics by charged-pion correlations
  The environment generated in the mid-rapidity region of a high-energy nuclear collision endows the pionic degrees of freedom with a time-dependent effective mass. Its specific evolution provides a mechanism for the production of back-to-back charge-conjugate pairs of soft pions which may present an observable signal of the non-equilibrium dynamics of the chiral order parameter. 
Jorgen Randrup (Lawrence Berkeley Laboratory, California, USA)