Nuclear Physics Seminar

Measurements of dN/dy for pions by the BRAHMS collaboration at RHIC have shown little indication for a broad plateau-like rapidity distribution as characteristic for the Bjorken scenario of fireball expansion. In contrast, the data seem to be described well by the Landau scenario which assumes complete stopping of the colliding nuclei. However, Bjorken expansion is an assumption underlying many models used to describe heavy-ion collision dynamics. I review some differences between these two extreme scenarios and introduce a model which can be tuned to reproduce both cases. This model is able to simultaneously describe single particle spectra and two particle
correlations, but only if the assumption of Bjorkenness is relaxed, one of the possible clues to the so-called HBT puzzle. I suggest how measuring the rapidity dependence of hard thermal photons can directly be used to distinguish between Bjorken and Landau dynamics.