Event plane determination from the zero degree calorimeter at the cooling storage ring external-target experiment

The Cooling Storage Ring external-target experiment(CEE)spectrometer is used to study the nuclear matter created in heavy-ion collisions at√sNN=2.1-2.4 GeV with the aim to reveal the quantum chromodynamics phase structure in the high-baryon-density region.Collective flow is considered an effective probe for evaluating the properties of media during high-energy nuclear collisions.One of the main functions of the zero-degree calorimeter(ZDC),a subdetector system in the CEE,is to determine the reaction plane in heavy-ion collisions.This step is crucial for measuring the collective flow and other reaction-plane-related analyses.In this paper,we illustrate the procedures for event plane determination using the ZDC.Finally,isospin-dependent quantum molecular dynamics model-based predictions of the rapidity dependence of the directed and elliptical flows for p,d,t,3He,and 4He,produced in 2.1 GeV U+U collisions,are presented.

Anisotropic flow in high baryon density region

Collective flow is a powerful tool used to analyze the properties of a medium created during high-energy nuclear collisions.Here,we report a systematic study of the first two Fourier coefficients v_(1)and v_(2)of the proton andπ^(+)from Au+Au collisions in the energy range√sNN=2.11-4.9 GeV within the framework of a hadronic transport model(UrQMD).Recent results from the STAR experiment were used to test the model calculations.A meanfield mode with strong repulsive interaction is needed to reproduce the 10-40%data at 3 GeV.This implies that hadronic interactions play an important role in the collective flow development in the high baryon density region.The mean values of the freeze-out time for protons andπ^(+)are shifted earlier owing to the additional repulsive interactions.We predict the energy dependence of the mean values of the transverse momentum<pT>,v_(1),and v_(2)for both protons andπ^(+)from the Au+Au collisions.