Directed flow of transported and nontransported protons in Au + Au collisions from an ultrarelativistic quantum molecular dynamics model

摘要

The directed flow of inclusive, transported and nontransported (including produced) protons, as well asnantiprotons, has been studied in the framework of an ultrarelativistic quantum molecular dynamics approach fornAu + Au collisions atn√nsNN = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV. The rapidity, centrality, and energyndependence of directed flow for various proton groups are presented. It is found that the integrated directed flowndecreases monotonically as a function of collision energy forn√nsNN = 11.5 GeV and beyond. However, the signnchange of directed flow of inclusive protons, seen in experimental data as a function of centrality and collisionnenergy, can be explained by the competing effect of directed flowbetween transported and nontransported protons.nSimilarly, the difference in directed flow between protons and antiprotons can be explained. Our study offers anconventional explanation on the cause of the v1 sign change other than the antiflow component of protons alone,nwhich is argued to be linked to a phase transition.