Within the framework of the UrQMD model, by tracing the number of initial quarks in protons, we study the elliptic flow of protons with 3, 2, 1, 0 initial quarks and anti-protons in Au+Au collisions at SNN^(1/2)= 7.7,...Within the framework of the UrQMD model, by tracing the number of initial quarks in protons, we study the elliptic flow of protons with 3, 2, 1, 0 initial quarks and anti-protons in Au+Au collisions at SNN^(1/2)= 7.7, 11.5, 39,200 GeV. The difference of elliptic flow between protons with 2, 1, 0 initial quarks and anti-protons is smaller than 0,or consistent with 0, respectively. The difference of elliptic flow between transported protons(with 3 initial quarks)and anti-protons is larger than 0 at 7.7, 11.5 and 39 GeV. This is in good agreement with the STAR results at 7.7 and 11.5 GeV, but overestimates the STAR results at 39 GeV. The yield of transported protons with 3 initial quarks is smaller than of protons with 2 and 1 initial quarks, and v_2 of all protons is much smaller than the STAR results. The observation of the v_2 difference of elliptic flow between transported protons and anti-protons in the UrQMD model partly explains the difference between protons and anti-protons observed in the Beam Energy Scan program at the Relativistic Heavy Ion Collider(RHIC).展开更多
A potential version of the UrQMD(UrQMD/M) transport model and a traditional coalescence model are combined to calculate the production of ~3He fragments in central Pb+Pb collisions at SPS energies 20-80 Ge V/nucleon. ...A potential version of the UrQMD(UrQMD/M) transport model and a traditional coalescence model are combined to calculate the production of ~3He fragments in central Pb+Pb collisions at SPS energies 20-80 Ge V/nucleon. It is found that the Lorentz transformation in the afterburner influences visibly the ~3He yield and should be considered in calculations. The rapidity distribution of ~3He multiplicities(including the concave shape) can be described well with Ur QMD/M when it stops during t_cut=(100±25) fm/c and the coalescence afterburner with one parameter set of(R_0,P_0)=(3.8 fm, 0.3 Ge V/c) is taken into use afterwards.展开更多
The time evolution of both proton and anti-proton v_2 flows from Au+Au collisions at (S_NN)^(1/2)=7.7 Ge V are examined by using both pure cascade and mean-field potential versions of the Ur QMD model. Due to a strong...The time evolution of both proton and anti-proton v_2 flows from Au+Au collisions at (S_NN)^(1/2)=7.7 Ge V are examined by using both pure cascade and mean-field potential versions of the Ur QMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller v_2 values.Therefore, the experimental data of anti-proton v_2 as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD.展开更多
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 ...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.展开更多
By considering different values of the time-step for the potential updates in the ultra-relativistic quantum molecular dynamics(UrQMD) model, we examine its influence on observables, such as the yield and collective f...By considering different values of the time-step for the potential updates in the ultra-relativistic quantum molecular dynamics(UrQMD) model, we examine its influence on observables, such as the yield and collective flow of nucleons and pions from heavyion collisions around 1 GeV/nucleon. It is found that these observables are affected to some extent by the choice of the time-step,and the impact of the time-step on the pion-related observables is more visible than that on the nucleon-related ones. However,its effect on the π-/π+yield ratio and elliptic flow difference between neutrons and protons, which have been taken as sensitive observables for probing the density-dependent nuclear symmetry energy at high densities, is fairly weak.展开更多
I discuss the results from a study of the central ^12CC collisions at 4.2 A GeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativist...I discuss the results from a study of the central ^12CC collisions at 4.2 A GeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses. I found that the behavior of the nearest neighbor spacing distribution for the protons, neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data. I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.展开更多
Rapidity distributions of both E895 proton data at AGS energies and NA49 net proton data at SPS energies can be described reasonably well with a potential version of the Ur QMD in which mean-field potentials for both ...Rapidity distributions of both E895 proton data at AGS energies and NA49 net proton data at SPS energies can be described reasonably well with a potential version of the Ur QMD in which mean-field potentials for both pre-formed hadrons and confined baryons are considered, with the help of a traditional coalescence afterburner in which one parameter set for both relative distance R_0 and relative momentum P_0,(3.8 fm, 0.3 Ge V/c), is used. Because of the large cancellation between the expansion in R_0 and the shrinkage in P_0 through the Lorentz transformation, the relativistic effect in clusters has little effect on the rapidity distribution of free(net) protons. Using a Woods-Saxon-like function instead of a pure logarithmic function as seen by FOPI collaboration at SIS energies, one can fit well both the data at SIS energies and the Ur QMD calculation results at AGS and SPS energies. Further, it is found that for central Au+Au or Pb+Pb collisions at top SIS, SPS and RHIC energies, the proton fractions in clusters are about33%, 10%, and 0.7%, respectively.展开更多
The time evolution of protons and 3He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 Ge V/nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics（Ur QMD） model...The time evolution of protons and 3He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 Ge V/nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics（Ur QMD） model combined with the traditional coalescence afterburner. In the coalescence process, the relative distance R0 and relative momentum P0 are surveyed in the range of 3-4 fm and 0.25-0.35 Ge V/c, respectively. For both clusters, a strong reversed correlation between R0 and P0is seen and it is time-dependent as well. For protons, the accepted（R0, P0） bands lie in the time interval 30-60 fm/c, while for 3He, a longer time evolution（at about 60-90 fm/c） is needed. Otherwise, much smaller R0 and P0values should be chosen. If we further look at the rapidity distributions from both central and semi-central collisions, it is found that the accepted [tcut,（R0, P0）] assemble can provide consistent results for proton yield and collective flows especially at mid-rapdities, while for 3He, the consistency is destroyed at both middle and projectile-target rapidities.展开更多
基金Supported in part by the MoST of China 973-Project(2015CB856901)National Natural Science Foundation of China(11890711)self-determined research funds of CCNU from the colleges’ basic research and operation of MOE(CCNU18TS031)
文摘Within the framework of the UrQMD model, by tracing the number of initial quarks in protons, we study the elliptic flow of protons with 3, 2, 1, 0 initial quarks and anti-protons in Au+Au collisions at SNN^(1/2)= 7.7, 11.5, 39,200 GeV. The difference of elliptic flow between protons with 2, 1, 0 initial quarks and anti-protons is smaller than 0,or consistent with 0, respectively. The difference of elliptic flow between transported protons(with 3 initial quarks)and anti-protons is larger than 0 at 7.7, 11.5 and 39 GeV. This is in good agreement with the STAR results at 7.7 and 11.5 GeV, but overestimates the STAR results at 39 GeV. The yield of transported protons with 3 initial quarks is smaller than of protons with 2 and 1 initial quarks, and v_2 of all protons is much smaller than the STAR results. The observation of the v_2 difference of elliptic flow between transported protons and anti-protons in the UrQMD model partly explains the difference between protons and anti-protons observed in the Beam Energy Scan program at the Relativistic Heavy Ion Collider(RHIC).
基金the National Natural Science Foundation of China(Grant Nos.11375062,11275068,11505056,and 11505057)the project sponsored by SRF for ROCS,SEM,the Education Bureau of Zhejiang Province(Grant No.Y201533176)the Doctoral Scientific ResearchFoundation(Grant No.11447109)
文摘A potential version of the UrQMD(UrQMD/M) transport model and a traditional coalescence model are combined to calculate the production of ~3He fragments in central Pb+Pb collisions at SPS energies 20-80 Ge V/nucleon. It is found that the Lorentz transformation in the afterburner influences visibly the ~3He yield and should be considered in calculations. The rapidity distribution of ~3He multiplicities(including the concave shape) can be described well with Ur QMD/M when it stops during t_cut=(100±25) fm/c and the coalescence afterburner with one parameter set of(R_0,P_0)=(3.8 fm, 0.3 Ge V/c) is taken into use afterwards.
基金the National Natural Science Foundation of China(Grant Nos.1137506211547312,and 11275068)the project sponsored by SRF for ROCS,SEM,and the Doctoral Scientific Research Foundation(Grant No.11447109)
文摘The time evolution of both proton and anti-proton v_2 flows from Au+Au collisions at (S_NN)^(1/2)=7.7 Ge V are examined by using both pure cascade and mean-field potential versions of the Ur QMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller v_2 values.Therefore, the experimental data of anti-proton v_2 as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD.
基金supported by the National Key Research and Development Program of China (No. 2020YFE0202002)the National Natural Science Foundation of China [Nos. 11890710(11890711) and 12175084]
文摘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.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11505057, 11547312, 11375062, and 11605270)the Department of Education of Zhejiang Province (Grant No. Y201533176)+1 种基金the China Postdoctoral Special Science Foundation (Grant No. 2016M591730)support by the computing server C3S2 in Huzhou University
文摘By considering different values of the time-step for the potential updates in the ultra-relativistic quantum molecular dynamics(UrQMD) model, we examine its influence on observables, such as the yield and collective flow of nucleons and pions from heavyion collisions around 1 GeV/nucleon. It is found that these observables are affected to some extent by the choice of the time-step,and the impact of the time-step on the pion-related observables is more visible than that on the nucleon-related ones. However,its effect on the π-/π+yield ratio and elliptic flow difference between neutrons and protons, which have been taken as sensitive observables for probing the density-dependent nuclear symmetry energy at high densities, is fairly weak.
文摘I discuss the results from a study of the central ^12CC collisions at 4.2 A GeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses. I found that the behavior of the nearest neighbor spacing distribution for the protons, neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data. I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.
基金the National Natural Science Foundation of China(Grant Nos.1137506211547312 and 11275068)+2 种基金the project sponsored by SRF for ROCSSEMand the Doctoral Scientific Research Foundation(Grant No.11447109)
文摘Rapidity distributions of both E895 proton data at AGS energies and NA49 net proton data at SPS energies can be described reasonably well with a potential version of the Ur QMD in which mean-field potentials for both pre-formed hadrons and confined baryons are considered, with the help of a traditional coalescence afterburner in which one parameter set for both relative distance R_0 and relative momentum P_0,(3.8 fm, 0.3 Ge V/c), is used. Because of the large cancellation between the expansion in R_0 and the shrinkage in P_0 through the Lorentz transformation, the relativistic effect in clusters has little effect on the rapidity distribution of free(net) protons. Using a Woods-Saxon-like function instead of a pure logarithmic function as seen by FOPI collaboration at SIS energies, one can fit well both the data at SIS energies and the Ur QMD calculation results at AGS and SPS energies. Further, it is found that for central Au+Au or Pb+Pb collisions at top SIS, SPS and RHIC energies, the proton fractions in clusters are about33%, 10%, and 0.7%, respectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.11375062,11547312,11275068,11505056 and11505057)SRF for ROCS,SEM and the Doctoral Scientific Research Foundation(Grant No.11447109)
文摘The time evolution of protons and 3He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 Ge V/nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics（Ur QMD） model combined with the traditional coalescence afterburner. In the coalescence process, the relative distance R0 and relative momentum P0 are surveyed in the range of 3-4 fm and 0.25-0.35 Ge V/c, respectively. For both clusters, a strong reversed correlation between R0 and P0is seen and it is time-dependent as well. For protons, the accepted（R0, P0） bands lie in the time interval 30-60 fm/c, while for 3He, a longer time evolution（at about 60-90 fm/c） is needed. Otherwise, much smaller R0 and P0values should be chosen. If we further look at the rapidity distributions from both central and semi-central collisions, it is found that the accepted [tcut,（R0, P0）] assemble can provide consistent results for proton yield and collective flows especially at mid-rapdities, while for 3He, the consistency is destroyed at both middle and projectile-target rapidities.
