The QGP-Stall or Not ?

In 1996, D.H. Rischke and M. Gyulassy proposed to use the time-delay signal in Bose-Einstein correlations (BEC) as a signature for the possible formation of a quark-gluon plasma (QGP) in relativistic heavy-ion collisions. In particular, they suggested to measure the ratio of the transversal interferometry radii, $R_{out}/R_{side}$, which can be obtained by fitting experimental BEC data with a parametrization introduced by G. Bertsch et al. in 1988. The transverse radius parameter $R_{out}$ has compared to the transverse radius parameter $R_{side}$ an additional temporal dependence which should be sensitive to a prolonged lifetime of a fireball, in case a QGP was formed in a relativistic heavy-ion collision. This latter phenomenon is known under the term ``QGP stall''. In the following, I shall explain why I believe that the time-delay signal in Bose-Einstein correlations is not a good signature for the possible formation of a QGP.