Effects Of The Pion-nucleon Potential On The Collective Flow Of Pion

The equation of state of the hot and dense nuclear matter can reflect the energy dependence of the isospin asymmetry,temperature and nuclear matter density,which plays a crucial role in understanding diverse phenomena in nuclear structure and reaction,as well as in astrophysics.The study of the equation of nuclear matter has always been one of the hot topics in the field of nuclear physics.Heavy ion reaction is the only way to produce the hot and dense nuclear matter under laboratory conditions.Whereas,the time of the existence of the nuclear matter is so short that it is impossible to measure the characteristic of the nuclear matter in the laboratory.Combining the transport model with the experimental measurement is an effect way to obtain the information of the hot and dense matter.As the first meson produced in the heavy ion collisions,pion is an important probe to investigate the equation of state of dense nuclear matter.Within the framework of the ultrarelativistic quantum molecular dynamics(UrQMD)model,pion dynamics in heavy ion collisions at different energy has been invested.The motion of pion in nuclear medium can be influenced by the pion-nucleon potential.Based on the newly updated version of the ultrarelativistic quantum molecular dynamics(UrQMD)model,the collective flow and the transverse velocity distribution of pion are studied by employing two different pion-nucleon potentials.By comparison the simulated results with the FOPI experimental data,it is found that the directed flow of pion can be reproduced well by calculations with a relatively weak pion-nucleon potential.In this passage,a better description of FOPI experimental data of the pion flow as the function of both rapidity and centrality has obtained with the consideration of the weakly attractive pion potential.The study of the pion flow provides a necessary conditions for obtaining the relevant information of the nuclear matter.