Improvement Of Hadronization Algorithm In Transport Simulations Of Relativistic Heavy-ion Collisions

The current mainstream view is that our universe evolved from an singularity with infinite density and infinite temperature through explosions.Within a few microseconds after the Big Bang,the entire universe is composed of the quark gluon plasma(QGP).According to Quantum Chromodynamics(QCD),quarks are confined in hadrons by strong interactions,so humans have not observed free quarks so far.In order to achieve quark confinement,scientists built a relativistic heavy ion collider to create the hightemperature and high-pressure environment required for quark confinement.In theory,QGP can be generated by accelerating two atomic nuclei close to the speed of light.Because QGP exists for a very short time,only the properties of the particles in the final state after the collision can be observed experimentally,and no information about the intermediate process can be detected directly.A multiphase transport(AMPT)model has been widely used in studying the dynamics of relativistic heavy-ion collisions and the properties of QGP.In the string melting version of the AMPT model,the hadronization algorithm has been improved by favoring parton combinations close in not only coordinate space but also momentum space.Formation probabilities of mesons,baryons,and antibaryons during hadronization are determined by their corresponding Wigner functions for the valence parton combinations with no free parameters,and the net baryon,electric,and strangeness charges are conserved during quark coalescence.In this article we have extensively discussed the effect of hadronization on anisotropic flows.The baryon directed flow is considered to be related to the first-order phase transition in the QCD phase diagram,which can provide important information on the critical point of the phase transition.An improved hadronization algorithm based on the Wigner function qualitatively reproduces the collision energy dependence of the proton directed flow slope experimentally observed.In addition,the new hadronization algorithm can also describe the relative particle ratio reasonably well.Recently,the ALICE Collaboration have measured the dihadron correlations in p + p pcollisions at (?)=7 TeV.At the near side,it was found that the meson-meson correlation exhibits an expected peak,while the baryon-baryon and antibaryon-antibaryon correlations show an anticorrelation structure.It was argued that this phenomenon can be related to the baryon production mechanisms in the fragmentation process.The AMPT model with the improved hadronization algorithm can reproduce the baryon-baryon and antibaryon-antibaryon anti-correlations at the near side.