We use the string melting version of a multi-phase transport (AMPT) model to study Cu+Au collisions at $\sqrt{s_{NN}}=200$ GeV. The rapidity distributions of identified hadrons show asymmetric dependences on rapidity. In addition, elliptic and triangular flows at mid-rapidity from the AMPT model for pions, kaons, and protons agree reasonably with the experimental data up to $p_{T}\sim1$ GeV$/c$. We then investigate the forward/backward asymmetry of $v_2$ and $v_3$. We find that these anisotropic flows are larger on the Au-going side than the Cu-going side, while the asymmetry tends to go away in very peripheral collisions. We also make predictions on transverse momentum spectra of identified hadrons and longitudinal decorrelations of charged particles, where the average decorrelation of elliptic flow in asymmetric Cu+Au collisions is found to be stronger than that in Au+Au collisions.
Correlations between azimuthal anisotropy Fourier harmonics $v_{n}$ ($n = 2, 3, 4$) are studied using the events from PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}}=2.76$ TeV generated by the HYDJET++ and AMPT models, and compared to the corresponding experimental results obtained by the ATLAS Collaboration. The Fourier harmonics $v_{n}$ are measured over a wide centrality range using the two-particle azimuthal correlation method. The slopes of the $v_{2}$--$v_{3}$ correlation from both models are in a good agreement with the ATLAS data. The HYDJET++ model predicts a stronger slope for the $v_{…
Transverse Spherocity is an event structure variable which provide an effective way to disentangle the data into hard and soft components of the processes corresponding to events with small and large numbers of multi-parton interactions (MPI), respectively. Recent experimental results in small systems from the LHC suggest the importacnce of transverse spherocity variable in the classification of the events. In this contribution, we have studied the dynamics of identified particle production in Xe-Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV using A Multi-Phase Transport Model (AMPT) and the rec…
To reduce the effect of the fluctuations of initial geometrical shape, elliptic flow are studied at fixed centrality in Au+Au collision at $\sqrt{s_{\rm NN}}$=200GeV. It is observed with the participant increasing, elliptic flow has an increase and a decrease at different fixed impact parameter, but not a trivial fluctuation. It is analyzed that the initial space anisotropy dominates the participant dependence of elliptic flow in near-central collisions(b=5fm) and mid-central collisions(b=8fm), while the interaction between particles can mainly answer for the behavior of elliptic flow in perip…
Event-by-event fluctuations in the spatial patterns in charged particles generated in Pb--Pb collisions at the center-of-mass energy $\sqrt{S_{\rm{NN}}}$ = 2.76 TeV are studied within A MultiPhase Transport (AMPT) model. The spatial patterns of the particles generated in the ($η, ϕ$) space for $|η| \le 0.8$ are studied using the methodology of intermittency and erraticity analysis. We find negative intermittency for charged particles generated in a range of $p_{\rm{T}}$ windows. This result contrasts sharply from what is expected for a quark-gluon plasma undergoing hadronization by a second-or…
In this paper, we study and predict the charged-particle pseudorapidity multiplicity density ($\frac{dN_{ch}}{dη}$), transverse momentum spectra of identified particles and their ratios in relativistic heavy ion collisions at the Large Hadron Collider (LHC), using the string-melting version of a multi-phase transport (AMPT) model with improved quark coalescence method. Results of the charged-particle pseudorapidity multiplicity density from AMPT model calculations for Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are compared with the experimental data. Good agreements are generally found betwe…
The multiplicity fluctuations are sensitive to QCD phase transition and to the presence of critical point in QCD phase diagram. At critical point a system undergoing phase transition is characterized by large fluctuations in the observables which is an important tool to understand the dynamics of particle production in heavy-ion interactions and phase changes. Multiplicity fluctuations of produced particles is an important observable to characterize the evolving system. Using scaling exponent obtained from the normalized factorial moments of the number of charged hadrons in the two dimensional…
The elliptic flow ($v_{2}$) at $\sqrt{s_{\rm NN}} = $ 11.5, 39, and 200 GeV and triangular flow ($v_{3}$) at $\sqrt{s_{\rm NN}} = $ 200 GeV of identified particles ($π^{\pm}, K^{\pm}, K^{0}_{S}, p, \bar{p}, ϕ, Λ$ and $\barΛ$) from 0\%--80\% central Au+Au collisions are analyzed using a multiphase transport (AMPT) model. It is shown that the experimental results from the $η$-sub event plane method can be reproduced with a parton scattering cross section between 1.5 and 3 mb. We also studied the differential and integrated $v_{2}/v_{3}$ ratios and conclude that they are anti-corrected with the p…
Higher-order cumulants of the distributions of conserved charges, such as net-baryon number, are sensitive to the quantum chromodynamics(QCD) phase transition and the QCD critical point. We calculate the cumulants and correlation functions of proton, antiproton, and net-proton multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}} = 7.7$ GeV using a multiphase transport model(AMPT). The AMPT model can basically describe the trends of cumulants, cumulant ratios, (normalized) correlation functions of the proton and net-proton measured by the STAR experiment. The multiproton (baryon) co…
A compilation of recently measured STAR data for elliptic flow ($v_{2}$) of $ϕ$ mesons in RHIC Beam Energy Scan program and comparison with a multiphase transport model (AMPT) has been presented. The experimental data at $\sqrt{s_{NN}}$ $\geq$ 19.6 GeV agrees well with string melting version of the AMPT model. The model includes partonic interactions and quark coalescence as a mechanism of hadronization. This indicates that there is a substantial contribution to collectivity from partonic interactions at $\sqrt{s_{NN}}$ $\geq$ 19.6 GeV. The measured $ϕ$-meson $v_{2}$ at $\sqrt{s_{NN}}$ = 7.7 a…
In this paper we have shown theoretical model comparisons with ALICE results for average D mesons (D$^0$, D$^+$, D$^{*+}$ and $D^+_s$) in $p$+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV for various centralities. Transport calculations of AMPT and calculations from heavy quark pQCD model, NLO(MNR) have been used for the study of $p_T$ dependent nuclear modification factors in terms of collision centrality ($\displaystyle{Q_{pPb}}$) and the central-to-peripheral ratios ($\displaystyle{Q_{cp}}$) of D mesons. It is found that NLO model with its parametrized $\displaystyle{k_T}$ broadening scheme p…
Based on an improved multiphase transport (AMPT) model, which gives a good description of proton production with a smooth quark matter to hadronic matter transition in relativistic heavy ion collisions, we study deuteron and triton production from the coalescence of nucleons at the kinetic freezeout of these collisions. For Au+Au collisions at center-of-mass energies $\sqrt{s_\text{NN}}$ from 7.7 GeV to 200 GeV available at the Relativistic Heavy Ion Collider (RHIC), we find that the yield ratio $N_\text{t}N_\text{p}/N_\text{d}^2$ of proton, deuteron\com{,} and triton is essentially a constant…
Predictions for Identified Hadron ($π^\pm$, $K^\pm$ and $p(\overline{p})$) Production and Collective Dynamics in Oxygen-Oxygen Collisions at $\sqrt{s_{NN}}$= 7 TeV with EPOS4, AMPT-SM, and Angantyr in Pythia 8
本文用 EPOS4、AMPT-SM 与 Pythia8/Angantyr 预测 7 TeV 氧–氧碰撞中 π、K、质子的产额、谱和集体行为，并比较三者的流效应差异。
Fluctuations in the initial transverse energy-density distribution lead to anisotropic flows as observed in central high-energy heavy-ion collisions. Studies of longitudinal fluctuations of the anisotropic flows can shed further light on the initial conditions and dynamical evolution of the hot quark-gluon matter in these collisions. Correlations between anisotropic flows with varying pseudorapidity gaps in Pb+Pb collisions at the CERN Large Hadron Collider are investigated using both an event-by-event (3+1)-D ideal hydrodynamical model with fluctuating initial conditions and the a multiphase …
We study the production of pions, kaons, and (anti)protons in A Multi Phase Transport (AMPT) Model in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 27, and 200 GeV. We present the centrality and energy dependence of various bulk observables such as invariant yields as a function of transverse momentum $p_T$, particle yields $dN/dy$, average transverse momentum $\langle p_T \rangle$, and various particle ratios, and compare them with experimental data. Both default and string melting (SM) versions of the AMPT model are used with three different sets of initial conditions. We observe that neither th…
Impact of particle production mechanisms on pseudorapidity distribution and directed flow in Au+Au and Cu+Cu collisions at $\sqrt{s_{NN}}$ = 19.6 GeV using AMPT model
We perform a systematic study on the decorrelation of anisotropic flows along the pseudorapidity in relativistic heavy-ion collisions at the LHC and RHIC energies. The dynamical evolution of the QGP fireball is simulated via the CLVisc (ideal) (3+1)-dimensional hydrodynamics model, with the fully fluctuating initial condition from A-Multi-Phase-Transport (AMPT) model. Detailed analysis is performed on the longitudinal decorrelations of elliptic, triangular and quadrangular flows in terms of flow vectors, flow magnitudes and flow orientations (event planes). It is found that pure flow magnitude…
The multiplicity and elliptic flow of charged particles produced in Pb-Pb collisions at center of mass energy $\sqrt{s_{NN}}=2.76$ TeV from the Large Hadron Collider are studied in a multiphase transport (AMPT) model. With the standard parameters in the HIJING model, which is used as initial conditions for subsequent partonic and hadronic scatterings in the AMPT model, the resulting multiplicity of final charged particles at mid-pseudorapidity is consistent with the experimental data measured by the ALICE Collaboration. This value is, however, increased by about 25% if the final-state partonic…
The mass ordering of $v_{2}^{hadron}$ is regarded as one of the key signatures of collective behaviour in ultra relativistic heavy ion collisions. This observation has been found to be in compliance with the hydrodynamical response of a strongly interacting system to the initial spatial anisotropy. Flow co-efficients measured with identified particles in p-Pb/d-Au collisions have shown similar mass-splitting of $v_{2}^{hadron}$ indicating towards the presence of collective dynamics in small collision systems. Arguably, small size in the overlap geometry of such colliding systems may not be sui…
Recent data from p+p and p+Pb collisions at the Large Hadron Collider (LHC), and d+Au and $^3$He+Au collisions at the Relativistic Heavy Ion Collider (RHIC) reveal patterns that---when observed in the collision of heavy nuclei---are commonly interpreted as indicators of a locally equilibrated system in collective motion. The comparison of these data sets, including the forthcoming results from p+Au and p+Al collisions at RHIC, will help to elucidate the geometric dependence of such patterns. It has recently been shown that A-Multi-Phase-Transport-Model (AMPT) can describe some of these feature…
By the sample generated by the AMPT with string melting model, we compare the azimuthal distributions of multiplicity, total transverse rapidity, and mean transverse rapidity. It is demonstrated that the azimuthal distribution of mean transverse rapidity is a good probe of the radial kinetic expansion. The anisotropic part of the distribution characterizes the anisotropic nature of the radial expansion, and isotropic part is combinations of thermal motion and isotropic radial expansion.
We carry out simulations using a multiphase transport (AMPT) model to describe the observed flow signatures in $\sqrt{s_{NN}}=2.76$ TeV Pb-Pb collisions. Especially, we calculate the flow fluctuations of $v_2$ in terms of cumulant ratios and the standardized skewness. Based on event-by-event AMPT simulations, we study the linear and cubic response relation between $v_2$ and $\varepsilon_2$. We found that the observed response relation is compatible to what has been noticed in hydrodynamic modelings, with similar dependence on shear viscosity. Besides, this response relation is not sensitive to…
We report recent results from a multiphase transport (AMPT) model on the azimuthal anisotropies of particle momentum distributions in heavy ion collisions at the Relativistic Heavy Ion Collider. These include higher-order anisotropic flows and their scaling, the rapidity dependence of anisotropic flows, and the elliptic flow of charm quarks.
Xe+Xe collisions at relativistic energies provide us with an opportunity to study a possible system with deconfined quarks and gluons, whose size is in between those produced by p+p and Pb+Pb collisions. In the present work, we have used AMPT transport model with nuclear deformation to study the identified particle production such as ($π^{+}+π^{-}$), (K$^{+}$+K$^{-}$), $\rm{K}_{s}^0$, (p+$\bar{\rm{p}}$), $ϕ$ and ($Λ+ \barΛ$) in Xe+Xe collisions at $\sqrt{s_{\rm NN}}$=5.44 TeV. We study the $p\rm{_T}$-spectra, integrated yield, $p\rm{_T}$-differential and $p\rm{_T}$-integrated particle ratios t…
Using a multi-phase transport model (AMPT) that includes both initial partonic and hadronic interactions, we study neighboring bin multiplicity correlations as a function of pseudorapidity in Au+Au collisions at $\sqrt{s_{NN}} = 7.7-62.4$ GeV. It is observed that for $\sqrt{s_{NN}} < $19.6GeV Au+Au collisions, the short-range correlations of final particles have a trough at central pseudorapidity, while for $\sqrt{s_{NN}} > $19.6GeV AuAu collisions, the short-range correlations of final particles have a peak at central pseudorapidity. Our findings indicate that the pseudorapidity dependence of…
Measurements of the dynamical correlations between neutral and charged kaons in central Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV by the ALICE Collaboration display anomalous behavior relative to conventional heavy-ion collision simulators such as AMPT, EPOS, and HIJING. We consider other conventional statistical models, none of which can reproduce the magnitude and centrality dependence of the correlations. The data can be reproduced by coherent emission from domains which grow in number and volume with increasing centrality. We show that the energy released by condensation of strange qu…
We calculate the cumulants and correlation functions of net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{NN}} = 7.7$ GeV using a multiphase transport model (AMPT) with both a new coalescence mechanism and all charge conservation laws. The AMPT model can qualitatively describe the centrality dependences of the net-kaon cumulants and cumulant ratios measured by the STAR experiment. By focusing on the stage evolution of the cumulants, cumulant ratios, and correlation functions, we reveal several key effects on the fluctuations and correlations of strangeness during the dynamic…
Driven by the Beam Energy Scan (BES) program at the RHIC, researches and discussions on the QCD phase diagram have flourished recently. In order to provide a reference from microscopic transport models, we performed a systematic analysis, using a multiphase transport (AMPT) model for the particle yields and a statistical model (THERMUS) for the thermal fit, for Au+Au collisions at $\sqrt{s_{\text{NN}}}$=7.7-200 GeV. It is found that at a fixed collision centrality the chemical freeze-out parameter, temperature $T_{\text{ch}}$, increases with collision energy and somehow saturates at certain va…
The correlation between the event mean-transverse momentum $[p_{\mathrm{T}}]$, and the anisotropic flow magnitude $v_n$, $ρ(v^{2}_{n},[p_{T}])$, has been argued to be sensitive to the initial conditions in heavy-ion collisions. We use simulated events generated with the AMPT and EPOS models for Au+Au at $\sqrt{\textit{s}_{NN}}$ = 200 GeV, to investigate the model dependence and the response and sensitivity of the $ρ(v^{2}_{2},[p_{T}])$ correlator to collision-system size and shape, and the viscosity of the matter produced in the collisions. We find good qualitative agreement between the correl…
From the events generated from the MC code of a multi-phase transport (AMPT) model with string melting, the properties of multiplicity fluctuations of charged particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=\rm{~2.76 \,TeV}$ are studied. Normalized factorial moments, $F_{q}$, of spatial distributions of the particles have been determined in the framework of intermittency. Those moments are found in some kinematic regions to exhibit scaling behavior at small bin sizes, but not in most regions. However, in relating $F_{q}$ to $F_{2}$ scaling behavior is found in nearly all regions. The …
A beam energy scan has been carried out at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory to search for the onset of deconfinement and a possible critical point where the transition from a Quark Gluon Plasma to a hadronic phase changes from a rapid cross-over to a first order phase transition. Anisotropy in the azimuthal distribution of produced particles such as the second and third harmonics $v_2$ and $v_3$ are expected to be sensitive to the existence of a Quark Gluon Plasma phase and the Equation of State of the system. For this reason, they are of great experimental…
We present theoretical model comparison with published ALICE results for D-mesons (D$^0$, D$^+$ and D$^{*+}$) in $p$+$p$ collisions at $\sqrt{s}$ = 7 TeV and $p$+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. Event generator HIJING, transport calculation of AMPT and calculations from NLO(MNR) and FONLL have been used for this study. We found that HIJING and AMPT model predictions are matching with published D-meson cross-sections in $p$+$p$ collisions, while both under-predict the same in $p$+Pb collisions. Attempts were made to explain the $R_{pPb}$ data using NLO-pQCD(MNR), FONLL and other abo…
Two dimensional low-$p_T$ dihadron correlations in azimuthal angle $ϕ$ and pseudo-rapidity $η$ in high-energy heavy-ion collisions are investigated within both the HIJING Monte Carlo model and an event-by-event (3+1)D ideal hydrodynamic model. Without final-state interaction and collective expansion, dihadron correlations from HIJING simulations have a typical structure from minijets that contains a near-side two-dimensional peak and an away-side ridge along the $η$-direction. In contrast, event-by-event (3+1)D ideal hydrodynamic simulations with fluctuating initial conditions from the HIJING+…
A multi-phase transport (AMPT) model has been successful in explaining a wide range of observables in relativistic heavy ion collisions. In this work, we implement a modern set of free proton parton distribution functions and an impact parameter-dependent nuclear shadowing in the AMPT model. After refitting the parameters of the two-component initial condition model to the experimental data on $pp$ and $p \bar p$ total and inelastic cross sections from $\sqrt s \sim $ 4 GeV to 13 TeV, we study particle productions in $pp$ and $AA$ collisions. We show that the updated AMPT model with string mel…
In this study, we systematically investigate deformed Xe-Xe collisions at 5.44 TeV center of mass energy. We exploit the Monte Carlo HYDJET++ model to compute transverse momentum ($p_{T}$) distribution, nuclear modification factor $R_{AA}$ and relative suppression in terms of $R_{CP}$ as a function of transverse momentum and centrality of collision of charged hadrons in body-body and tip-tip geometrical configurations, respectively. We have compared HYDJET++ model results to those from ALICE experimental data and AMPT model (String-Melting version) results. Minimum bias Xe-Xe collisions show a…
Transverse spherocity is an event shape observable having a very unique capability to separate the events based on their geometrical shapes. Recent results from experiments at the LHC suggest that transverse spherocity is an important event classifier in small collision systems. In this work, we use transverse spherocity for the first time in heavy-ion collisions and perform an extensive study on azimuthal anisotropy of charged particles produced in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV using A Multi-Phase Transport Model (AMPT). The azimuthal anisotropy is estimated using the 2-…
Pseudorapidity density, transverse momentum spectra, and elliptic flow studies in Xe-Xe collision systems at $\rm{\sqrt{s_{NN}} = 5.44 TeV}$ using the HYDJET++ model
Within a multi-phase transport (AMPT) model, dijet asymmetry is studied in Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV. It is found that a large dijet asymmetry ($A_{J}$) is produced by strong interactions between jets and partonic matter. It is demonstrated that hadronization and final-state hadronic rescatterings have little effects on $A_{J}$. The final $A_{J}$ is found to be driven by both initial $A_{J}$ and partonic jet energy loss, which is consistent with an increasing jet energy loss in a hot and strongly interacting partonic medium in more central Pb+Pb collisions.
We evaluate the effects of preequilibrium dynamics on observables in ultrarelativistic heavy-ion collisions. We simulate the initial nonequilibrium phase within A MultiPhase Transport (AMPT) model, while the subsequent near-equilibrium evolution is modeled using (2+1)-dimensional relativistic viscous hydrodynamics. We match the two stages of evolution carefully by calculating the full energy-momentum tensor from AMPT and using it as input for the hydrodynamic evolution. We find that when the preequilibrium evolution is taken into account, final-state observables are insensitive to the switchin…
Studies of beauty hadron and non-prompt charm hadron production in pp collisions at $\sqrt{s}$=13 TeV within a transport model approach
School of Mathematics and Physics, China University of Geosciences (Wuhan)（中国地质大学（武汉）数学与统计学院）；Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University（华中师范大学夸克与轻子物理教育部重点实验室及粒子物理研究所）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University（复旦大学理论核物理上海研究中心）
Anisotropic flow of hadronic matter is considered as a sensitive tool to detect the early stage dynamics of high-energy heavy-ion collisions. Taking the event by event fluctuations of the collision geometry into account, the elliptic flow parameter and the triangular flow parameter derived from the azimuthal distribution of produced hadrons, are investigated within the framework of a multiphase transport (AMPT) model, at a collision energy that in near future will typically be available at the Facility for Antiproton and Ion Research. The dependence of elliptic and triangular flow parameters o…
In high-energy heavy-ion collisions, structures in the initial collision zone are a matter of intense investigation, both from theory and experimental points of view. A large number of models have been developed to represent the initial state of the collision including Glauber model, Colour Glass Condensate (CGC) among others. Another important aspect of the study is to investigate proper observables that will be sensitive to the initial collision zone. In this work, we have discussed a formalism to implement the spatial clusters at the partonic level in the string melting version of the AMPT …
Baryon-strangeness correlation (C$_{BS}$) has been investigated with a multi-phase transport model (AMPT) in $^{197}$Au + $^{197}$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The centrality dependence of C$_{BS}$ is presented within the model, from partonic phase to hadronic matter. We find that the system still reserve partial predicted signatures of C$_{BS}$ after parton coalescence. But after hadronic rescattering, the predicted signatures will be obliterated completely. So it seems that both coalescence hadronization process and hadronic rescattering are responsible for the disappearance of…
Comment on "Evaluation of kinetic freeze-out properties in different relativistic heavy-ion collision systems at \sqrtsNN = 200 GeV'' (Eur. Phys. J. Plus (2025) 140:179) https://doi.org/10.1140/epjp/s13360-025-06119-0
Investigating forward-backward asymmetry in D-meson production and anisotropic flow in p-Pb collisions at the LHC
Wuhan Textile University（武汉纺织大学）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University（上海理论核物理中心，国家自然科学基金委员会与复旦大学）；Wuhan University of Technology（武汉理工大学）；China University of Geosciences (Wuhan)（中国地质大学（武汉））；East Carolina University（东卡罗来纳大学）；Institute of Modern Physics, Fudan University（复旦大学现代物理研究所）
