On elliptic flow and the blast-wave model

Abstract

Extensions of the blast-wave model for the description of non-central collisions are reviewed and the physics behind them is explained and illustrated. It is shown how the second-order anisotropy in expansion velocity together with the anisotropy in the shape or the density profile of the fireball determine the elliptic flow of the produced hadrons. Ambiguities and limitations of the models are discussed and different models are compared among themselves and with example data. It is concluded that model results should always be compared to $v_2(p_t)$ from several identified species in order to receive meaningful results about the freeze-out stage of the fireball and that even such a comparison may not be conclusive as the models may not be able to reproduce all relevant data.

Comments: 18 pages, 8 figures, minireview written for special volume of selected papers from the Zimanyi School 2023. New appendix added in the revised version on low-pt behaviour of v2. More explanatios added on some places. Results unchanged. Accepted in Int. J. Mod. Phys. A