Research On The Transverse Momentum Dependence Of The HBT Radii In Au + Au Collisions At RHIC Beam Energy Scan

Relativistic heavy ion collision mainly studies the quark gluon plasma(QGP),which is a nuclear matter produced at extreme high temperature and high energy density.obtaining the spatio-temporal structure and dynamics information of the source is the premise of studying QGP.In the experiment,because of the extremely short time and extremely high temperature of the reaction,it is impossible to obtain the spatio-temporal structure information of the source directly.Actually,people obtain the spatio-temporal structure and dynamic information by analyzing the end-state particles.The HBT correlation,also known as intensity interferometry,is an important means for people to obtain the spacetime and dynamics information of the source.It mainly uses the principle of identical of two final states to obtain the spatio-temporal information of the source by calculating the correlation function of the two-particle.In order to understand the results of the experiment of relativistic heavy ion collision,various models have been established.The multiphase transport model(AMPT)is a microscopic transport model that includes both partial sub-evolution and hadron evolution.In this paper,With the help of AMPT model,The transverse momentum dependence of HBT radii is studied by two-pion interferometry.especially,Transverse momentum dependence of the HBT radii is discussed for central Au + Au collisions at 11.5 GeV.It is found that different tranverses have different radii,and the HBT radii decreases with the increase of the tranverse.We think that the direct cause of the phenomenon is the single-particle momentum-space correlation.In order to verify the direct influence of single particle momentum-space correlation on the transverse momentum dependence of HBT radii,we broke the single-particle momentum-space correlation of pion mesons in the AMPT 11.5 GeV Au + Au collision event in two ways.one is intermingle The transverse momentum and transverse radii randomly,anoter is change the direction of tranverse momentum.The two-pion interferometry analysis is performed on the data without single particle momentum-space correlation.Since the source is expanded,the collective motion of the particles will eventually be reflected as the single-particle momentum-space correlation of the final particles.We use the Lorentz transformation to transform the fourmovement of the particle from the global coordinate system to the local coordinate system,removing the single-particle momentum-space correlation caused by the lateral expansion effect,and performing two-pion interference on the data without lateral expansion.In order to study the source scale,temperature and expansion velocity with the change of collision energy.We present a systematic analysis for the central Au + Au collisions at different collision energies.the HBT radii and its transverse momentum dependence is obtained by two-pion interferometry analysis.At the same time,the kinematic freezing temperature and the average expansion velocity of the source are obtained by analyzing the transverse mass spectra of pion meson,K meson and proton.It is found that in the energy region we studied,the source scale,temperature and expansion velocity do not change significantly with the increase of collision energy.