Transverse momentum dependence of directed particle flow at 160A GeV
Abstract
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,Δpt) 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,Δy) 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.
- Publication:
-
Physical Review C
- Pub Date:
- March 2001
- DOI:
- 10.1103/PhysRevC.63.034902
- arXiv:
- arXiv:nucl-th/0006056
- Bibcode:
- 2001PhRvC..63c4902Z
- Keywords:
-
- 25.75.Ld;
- 24.10.Lx;
- 24.10.Jv;
- Collective flow;
- Monte Carlo simulations;
- Relativistic models;
- Nuclear Theory;
- High Energy Physics - Phenomenology;
- Nuclear Experiment
- E-Print:
- REVTEX, 20 pages incl. 6 figures, revised and extended version