2000/06/30 by E. E. Zabrodin, E. Zabrodin, C. Fuchs +4
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph #nucl-ex #nucl-th
paper · pdf · doi:10.1103/physrevc.63.034902
published as Phys.Rev. C63 (2001) 034902 · REVTEX, 20 pages incl. 6 figures, revised and extended version
arxiv created 2000/10/20 · openalex publication_date 2001/02/21 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The transverse momentum (pt) dependence of hadron flow at SPS energies is studied. In particular, the nucleon and pion flow in S+S and Pb+Pb collisions at 160A GeV is investigated. For simulations the microscopic quark-gluon string model is applied. It is found that the directed flow of pions v1(y,\ensuremathΔpt) changes sign from a negative slope in the low-pt region to a positive slope at pt>~0.6 GeV/c as recently observed experimentally. The change of the flow behavior can be explained by early emission times for high-pt pions. We further found that a substantial amount of high-pt pions are produced in the very first primary nucleon-nucleon collisions at the surface region of the touching nuclei. Thus, at SPS energies high-pt nucleons seem to be a better probe for the hot and dense early phase of nuclear collisions than high-pt pions. Both in the light and in the heavy system the pion directed flow v1(pt,\ensuremathΔy) exhibits large negative values when the transverse momentum approaches zero, as also seen experimentally in Pb+Pb collisions. It is found that this effect is caused by nuclear shadowing. The proton flow, on the contrary, shows the typical linear increase with rising pt.