Search

Inspired by the BESIII newest observation of X(2370) glueball-like particle, we search its productions in both $e^+e^-$ collisions at $\sqrt{s}=$ 4.95 GeV and proton-proton (pp) collisions at $\sqrt{s}=$ 13 TeV with a parton and hadron cascade model PACIAE. In this model, the final partonic state (FPS) and the final hadronic state (FHS) are consecutively simulated and recorded. The X(2370) glueball- or tetraquark-state is then, respectively, recombined by two gluons or four quarks $ss\bar{s}\bar{s}$ in the FPS using the quantum statistical mechanics inspired dynamically constrained phase-space coalescence (DCPC) model. The X(2370) molecular-state is recombined by the baryon-antibaryon of $\Lambda$-$\bar{\Lambda}$ or $\Sigma$-$\bar{\Sigma}$, or by three mesons of $\pi^+\pi^{-}\eta'$, $K^+K^-\eta'$, or $K_S^0K_S^0\eta'$ in the FHS using DCPC model. In both $e^+e^-$ and pp collisions, significant discrepancies in the yields, the transverse momentum spectra and the rapidity distributions among the X(2370) glueball-, tetraquark-, and molecular-state are observed. These discrepancies are proposed as valuable criteria identifying the X(2370) different states from each other. Our results not only support the BESIII observation of glueball-like particle $\rm X(2370)$ production in $e^+e^-$ collisions, but also serve as a prediction for the $\rm X(2370)$ production in pp collisions. We strongly suggest the experimental measurement of the X(2370) glueball-like particle production in pp collisions at the LHC energies., Comment: 6 pages, 5 figures

The parton and hadron cascade model {\footnotesize PACIAE} is employed to confirm the BESIII newest observation of glueball-like particle $\rm X(2370)$ production in $e^+e^-$ collisions at $\sqrt{s}=4.95\,\mathrm{GeV}$. We coalesce the $\rm X(2370)$ glueball state with two gluons in the simulated partonic final state by the Dynamically Constrained Phase-space Coalescence ({\footnotesize DCPC}) model. Alternative configuration of $\rm X(2370)$ molecular state is recombined in the simulated hadronic final state with $\pi^{+},\pi^{-},K^{+}, K^{-},K_{S}^{0},K_{S}^{0}$ and $\eta'$ by {\footnotesize DCPC} model. The resulted particle transverse momentum spectrum and rapidity distribution, etc. show a significant discrepancy between the two states. They are not only serving as criteria to distinguish the $\rm X(2370)$ glueball state or molecular state, but also confirming the BESIII observation of glueball-like particle $\rm X(2370)$ productions in $e^+e^-$ collisions., Comment: 4 pages, 2 figures

The production of exotic hadron $\rm X(3872)$ in $pp$ collisions at $\sqrt{s}=2.76\,\mathrm{TeV}$ is investigated by the parton and hadron cascade model PACIAE in this work. In the simulation the final partonic state (quark matter, QM) and the final hadronic state (hadron matter, HM) are continuously processed and recorded. The $\rm X(3872)$ compact tetraquark state and loose molecular state are, respectively, coalesced and recombined in the QM and HM with the quantum statistical mechanics inspired dynamically constrained phase-space coalescence model. The formation time, velocity and temperature of QM (tetraquark state) and HM (molecular state) are proposed as identifying criteria between the two states. Our results in transverse momentum spectrum and rapidity distribution, etc. show a significant discrepancy between the two states and confirm that they are also valuable criteria identifying the $\rm X(3872)$ compact tetraquark state or molecular state., Comment: 6 pages, 3 figures

We introduce a parton and hadron cascade model PACIAE 3.0 based on PYTHIA 6.428 and the PACIAE 2.2 program series. The simulation framework of C-, B-, and A-loops are designed for the high energy ($\sqrt{s_{NN}}\geq 3$ GeV) and low energy ($\sqrt{s_{NN}}<3$ GeV) nuclear collisions, respectively, in PACIAE 3.0. In the C-loop simulation, the parton-parton inelastic scattering processes are added in the partonic rescattering process. The single string structure and multiple string interaction mechanism have been introduced investigating the strangeness enhancement in C- and B-loop. An improved mapping relation between the centrality percentage definition and the impact parameter definition is proposed responding the observation of $b_{max}\approx 20$ fm from ALICE, ATLAS, and CMS collaborations. We have extensively modified the phenomenological coalescence hadronization model. The PACIAE 3.0 model simulated results of particle yield, transverse momentum distribution, and rapidity distribution well reproduce, respectively, the experimental data measured at FOPI, E895, RHIC, and LHC energies., Comment: 15 pages, 15 figures

We calculate four types of initial vorticities in Au+Au collisions at energies $ \sqrt{S_{NN}} $ = 5--200 GeV using a microscopic transport model PACIAE. Our simulation shows the non-monotonic dependence of the initial vorticities on the collision energies. The energy turning point is around 10-15 GeV for different vorticities but not sensitive to impact parameter., Comment: 6 pages, 2 figures, 10th International Conference on New Frontiers in Physics (ICNFP 2021)

We improve the centrality definition in impact parameter in PACIAE model responding the fact reported by the ALICE, ATLAS, and CMS collaborations that the maximum impact parameter in heavy ion collisions should be extended to 20 $fm$. Meanwhile the PACIAE program is updated to a new version of PACIAE 2.2.2 with convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in one unified program version. The new impact parameter definition together with the optical Glauber model calculated impact parameter bin, $N_{part}$, and $N_{coll}$ in proton-nucleus and nucleus-nucleus collisions at relativistic energies are consistent with the improved MC-Glauber model ones within the error bar. The charged-particle pseudorapidity and the transverse momentum distributions in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV simulated by PACIAE 2.2.2 well reproduce the ALICE experimental data., Comment: 12 pages, 2 figures, 5 tables

The lepton charge asymmetry in $W^\pm$ production in the nuclear collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV is investigated with a parton and hadron cascade model PACIAE. Recently published ALICE and the ATLAS data of lepton charge asymmetry are well reproduced. An interesting linear scaling behavior is observed in the lepton charge asymmetry as a function of the collision system valence quark number asymmetry among the different size of nuclear collision systems at $\sqrt{s_{\rm NN}}=5.02$ TeV. This linear scaling behavior may serve as an additional constraint on the PDF (nPDF) extractions., Comment: 6 pages, 4 figures. arXiv admin note: text overlap with arXiv:2201.09525

We have systematically studied the connection between hadron and its quark component nuclear modification factors and the flavor (mass) ordering at both parton and hadron levels in the nucleus-nucleus collisions at the LHC energies by the PACIAE model. It turns out that these two physical phenomena explored in our last publication (J. Phys. G 49 065104, 2022) are generally held, irrespective of the rapidity, centrality, reaction energy, and the collision system size. The mass ordering at hadron level in nuclear modification factor seems to be really existed, which should be studied further both theoretically and experimentally., Comment: 7 pages, 12 figures

In this paper, the centrality dependent $\Zn$ and $\Wpm$ production and the isospin effect in $\Wpm$ production are investigated with a parton and hadron cascade model PACIAE in Pb--Pb collisions at $\sNN=5.02$~TeV. ALICE data of $\Zn$ production in Pb--Pb collisions at $\sNN=5.02$~TeV are found to be reproduced fairly well. The prediction on $\Wpm$ production in the same collision system is given as well. An interesting isospin effect is observed in exploring the charge asymmetry between $\Wp$ and $\Wm$ as a function of the asymmetry between number of valence $u$- and $d$-quarks varied from small to large collision systems at center-of-mass energy 5.02 TeV. The results serve as a important benchmarks for understanding the initial conditions of heavy-ion collisions., Comment: arXiv admin note: text overlap with arXiv:2002.00344

The exotic resonant state $P_{c}^{\pm}(4312)$, $P_{c}^{\pm}(4440)$, and $P_{c}^{\pm}(4457)$ are studied by using the dynamically constrained phase space coalescence DCPC model and PACIAE model in $pp$ collisions at $\sqrt{s}=7$, 13TeV, respectively. We consider exotic state $P_{c}^{\pm}(4312)$, $P_{c}^{\pm}(4440)$ and $P_{c}^{\pm}(4457)$ to be three kinds of possible structures, i.e. pentaquark state, the nucleus-like state, and the molecular state based on $P_c^\pm \to J/\psi{p}{(\bar p)}$ bound state. The yield, the transverse momentum distribution and the rapidity distribution of $P_{c}$ with three different structures are all predicted. The results indicated that the yield is on the order of $10^{-6}$, which might provide reference for experimental research., Comment: 6pages, 3 figures

We study the behavior of four types of vorticities in non-central Au+Au collisions at energies $\sqrt{S_{NN}}$ = 5--200 GeV using a microscopic transport model PACIAE. The results show that the vorticities decay faster at lower energy and smaller impact parameter. The non-monotonic dependence of the initial vorticities on the collision energies is reconfirmed and the turning point is 10-15 GeV for different vorticities. The global $\Lambda$ polarization at energies $\sqrt{S_{NN}}$ = 7.7--200 GeV is reproduced by introducing an energy density freeze-out criterion., Comment: 7 pages, 7 figures, to be published in Pyhysical Review C

The production of light (anti-)nuclei and (anti-)hypertriton in a recent collsion system size scan program proposed for the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) is investigated by using the dynamically constrained phase-space coalescence model and the parton and hadron cascade model. The collision system dependence of yield ratios for deuteron to proton, helium-3 to proton, and hypertriton to $\Lambda$-hyperon with the corresponding values for antiparticles is predicted. The work presents that for the yield ratios a significant difference exists between (hyper)nuclei and their anti-(hyper)nuclei. Besides, much more suppression for (anti-)hypernuclei than light (anti-)nuclei is present. We further investigate strangeness population factors $s_3$ as a function of atomic mass number $A$. Our present study can provide a reference for a upcoming collision system scan program at RHIC., Comment: 5 pages, 3 figures

We have used the dynamically constrained phase space coalescence model to study the production of the exotic state $X(3872)$ based on the hadronic final states generated by the parton and hadron cascade model (PACIAE) with $|y|<1$ and $p_T < 15.5$ GeV/c in $pp$ collisions at $\sqrt{s}=7$ and 13 TeV, respectively. Here the $X(3872)$ is assumed to consist of bound state $D\bar {D^*}$, which can form three possible structures for the tetraquark state, the nucleus-like state, and the molecular state. The yields of three different structures $X(3872)$ were predicted. The transverse momentum distribution and the rapidity distribution of three different structures $X(3872)$ are also presented. Sizable difference can be found in the transverse momentum and rapidity distributions for the three different $X(3872)$ structures., Comment: 6 pages, 3 figures

In this work, we propose a method to show the correspondence between hadron and its quark component nuclear modification factors. A parton and hadron cascade model PACIAE based on the PYTHIA6.4 is employed to calculate the hadron and its quark component nuclear modification factors in the 0-5\% most central $Pb+Pb$ collisions at $\sqrt{s_{NN}}$=2.76 TeV. It turns out that the hadron nuclear modification factor is usually smaller than that of its quark component. On the other hand, it is shown in our study that the "dead cone effect" is more likely to be identified with the quarks and mesons but not with the baryon states obviously., Comment: 6 pages, 5 figures

A dynamically constrained phase-space coalescence model plus PACIAE model was used to predict the exotic resonant state $Z_c^{\pm}(3900)$ yield, transverse momentum distribution, and the rapidity distribution with $|y| < 6$ and $p_T < 10$ GeV/c in $pp$ collisions at $\sqrt{s} = 1.96, 7$ and 13 TeV, respectively. The yield of the $Z_c^{\pm}(3900)$ is estimated to be around $10^{-6}$ to $10^{-5}$. We also present the energy dependence of the transverse momentum distributions and rapidity distributions for ${Z_c^{+}(3900)}$ and ${Z_c^{-}(3900)}$. The production of ${Z_c^{+}(3900)}$ and its anti-particle ${Z_c^{-}(3900)}$ is found to be quite similar to each other., Comment: 6 pages,5 figures

The production of $\rm{^3_\Lambda H}$ and $\rm{{^3_{\overline \Lambda}\overline H}}$, as well as $\rm{^3H}$, $\rm{{^3\overline H}}$, $\rm{^3He}$, and $\rm{{^3\overline {He}}}$ are studied in central collisions of isobars $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr at $\sqrt{s_{\rm{NN}}}=200$ GeV, using the dynamically constrained phase-space coalescence model and the {\footnotesize PACIAE} model with chiral magnetic effect. The yield, yield ratio, coalescence parameters, and strangeness population factor of (anti-)hypertriton and (anti-)nuclei produced in isobaric $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr collisions are predicted. The (anti-)hypertriton and (anti-)nuclei production is found to be insensitive to the chiral magnetic effects. Experimental data of Cu+Cu, Au+Au and Pb+Pb collisions from RHIC, LHC, and the results of {\footnotesize PACIAE+DCPC} model are presented in the results for comparison., Comment: 7 pages, 4 figures

We present a systematic study on the strange and multi-strange particles production in Pb+Pb collisions at $\sqrt{S_{NN}} = 2.76$ TeV based on the PACIAE model simulations. Two different mechanisms, namely the single string structure variations and multiple string interactions, are implemented in the simulations. These modifications give rise to an enhancement of the string tension value involved in the Lund string fragmentation framework and generate more strange particles in the hadronic final state. By comparing the simulation results with the ALICE experimental data, it turns out that the inclusion of the variable effective string tension in the PACIAE model is capable to reach an improved agreement between theory and experiment on the strangeness production in Pb+Pb collisions., Comment: 6 pages, 4 figures. arXiv admin note: text overlap with arXiv:1806.11390

In this paper, production of ${\rm W}^{\pm}$ and ${\rm Z}^{0}$ vector bosons in p-p, p-Pb (Pb-p), and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV is dynamically simulated with a parton and hadron cascade model PACIAE. ALICE data of ${\rm Z}^{0}$ production is found to be reproduced fairly well. A prediction for ${\rm W}^{\pm}$ production is given in the same collision systems, at the same energy and at the same energy. An interesting isospin-effect is observed in the sign-change of $\mu^{\pm}$ charge asymmetry in pp, pn, np, and nn collisions and in minimum bias p-Pb, Pb-p and Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV, respectively.

The production of strange particles $\Xi_{c}^{+}, K^{-}$ is simulated in mid-rapidity $pp$ collisions at $\sqrt{s}=7$ TeV with $0.2 \leq pt \leq 6$~GeV/c using the {\footnotesize PACIAE} model. The results are consistent with LHCb experimental data on $\Xi_{c}^{+}$ and $K^{-}$ yield. Then, a dynamically constrained phase-space coalescence ({\footnotesize DCPC}) model plus {\footnotesize PACIAE} model was used to produce the $\Xi_{c}^{+}K^{-}$ bound states and study the narrow excited $\Omega_{c}^{0}$ states through $\Omega_{c}^{0} \to \Xi_{c}^{+}K^{-}$ in $pp$ collisions at $\sqrt{s}=7$ and 13 TeV. The yield, transverse momentum distribution, and rapidity distribution of the five new excited $\Omega_{c}^{0}$ states of $\Omega_{c}(3000)^{0}$, $\Omega_{c}(3050)^{0}$, $\Omega_{c}(3066)^{0}$,$\Omega_{c}(3090)^{0}$and $\Omega_{c}(3119)^{0}$ were predicted., Comment: 6 pages, 4 figures

We propose a forward method, based on the PYTHIA6.4, to study theoretically the jet properties in the ultra-relativistic pp collisions. In the forward method, the partonic initial states are first generated with PYTHIA6.4 and then hadronized in the Lund srting fragmentation regime, and finally hadronic jets are constructed from the created hadrons. Jet properties calculated in the forward method for pp collisions at \sqrt{s}=7 TeV are comparable with the corresponding ones calculated with usual anti-k_t algorithm (backward method) in the PYTHIA6.4. The comparison between the results in the backward and forward methods may bring benefit to the understanding of the partonic origin of jets in the backward method., Comment: 6 pages, 5 figures

Production of the (anti)hypertriton nuclei $\rm ^3_{\Lambda}H$ and $\rm ^3_{\overline \Lambda}\overline H$ in Cu+Cu interactions at $\sqrt{s_{\rm{NN}}}=200$GeV is studied at three centrality bins of 0-10\%, 10-30\% and 30-60\% using the dynamically constrained phase-space coalescence model together with [PACIAE] model simulations. The $\rm ^3H(^3\overline H)$ and $\rm ^3He(^3\overline {He})$ nuclei has been compared. It is indicated by the study that the yields of light nuclei and hypernuclei increase rapidly from peripheral to central collisions while their anti-particle to particle ratios keep unchanged for different centrality bins. The strangeness population factor $S_3=\rm{{^3_{\Lambda}H}/({^3{He}}\times \Lambda/p)}$ was found to be close to unity, and was compatible with the STAR data and theoretical model calculation, suggesting that the phase-space population of strange quarks is similar with the ones of light quarks and the creation of deconfined high temperature quark matter in Cu+Cu collisions., Comment: 7 pages, 5 figures

We present a systematic study on the strange particle production at the Large Hadron Collider (LHC) in proton-proton (pp) collisions at $\sqrt{s}=$ 7 TeV based on PACIAE simulations. Two different mechanisms accounting for single string structure variations and multiple string interactions are implemented in the simulations. These modifications give rise to increased effective string tension in the Lund fragmentation model and generate more strange particles in the hadronic final state. By comparing the results with a wealth of the LHC data, it is turned out that the inclusion of variable effective string tension is capable to reach an improved agreement between theory and experiment, especially on the recently observed multiplicity dependence of strangeness enhancement in pp collisions. This approach provides us a new method to understand the microscopic picture of the novel high multiplicity pp events collected at the LHC in the string fragmentation framework.

The energy dependence of light (anti)nuclei and (anti)hypertriton production are investigated in central Au-Au collisions from AGS up to LHC energies at midrapidity, using the parton and hadron cascade model (PACIAE) together with the dynamically constrained phase-space coalescence model(DCPC). We find that the yields, yield ratios of the antiparticles to their corresponding particles, the coalescence parameters $B_A$ and the strangeness population factor $s_3$ of light (anti)nuclei and (anti)hypertriton strongly depend on the energy. Furthermore, we analyze and discuss the strangeness population factor $s_3$ and the coalescence parameters $B_A$, and find a transition point near by 20 GeV. These results thus suggest the potential usefulness of the $s_3$ and $B_A$ of light nuclei production in relativistic heavy-ion collisions as a direct probe of the transition point associated with the QCD critical phenomena. The results from PACIAE+DCPC model are well consistent with experimental data.

We employed the PYTHIA 6.4 model and the extended parton and hadron cascade model PACIAE 2.2 to comparatively investigate the DIS normalized specific charged hadron multiplicity in the 27.6 GeV electron semi-inclusive deep-inelastic scattering off proton and deuteron. The PYTHIA and PACIAE results calculated with default model parameters not well and fairly well reproduce the corresponding HERMES data, respectively. In addition, we have discussed the effects of the differences between the PYTHIA and PACIAE models., Comment: 8 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1412.7579

The parton and hadron cascade model PACIAE 2.1 (cf. Comput. Phys. Commun.184 (2013) 1476) has been upgraded to the new issue of PACIAE 2.2. By this new issue the lepton-nucleon and lepton-nucleus (inclusive) deep inelastic scatterings can also be investigated. As an example, the PACIAE 2.2 model is enabled to calculate the specific charged hadron multiplicity in the $e^-$+p and $e^-$+D semi-inclusive deep-inelastic scattering at 27.6 GeV electron beam energy. The calculated results are well comparing with the corresponding HERMES data. Additionally, the effect of model parameters \alpha and \beta in the Lund string fragmentation function on the multiplicity is studied., Comment: 15 pages, 4 figures

Based on the requirement in the simulation of lepton-nucleus deep inelastic scattering (DIS), we construct a fortran program LDCS 1.0 calculating the differential and total cross sections for the unpolarized charged lepton-unpolarized nucleon and neutrino-unpolarized nucleon neutral current (charged current) DIS at leading order. Any set of the experimentally fitted parton distribution functions could be employed directly. The mass of incident and scattered leptons is taken into account and the boundary conditions calculating the single differential and total cross section are studied. The calculated results well agree with the corresponding experimental data which indicating the LDCS 1.0 program is good. It is also turned out that the effect of tauon mass is not negligible in the GeV energy level., Comment: 23 pages, 9 figures, FORTRAN codes and readme files attached

We employed the new issue of a parton and hadron cascade model PACIAE 2.1 to systematically investigate the charged particle elliptic flow parameter $v_2$ in the relativistic nuclear collisions at RHIC and LHC energies. With randomly sampling the transverse momentum $x$ and $y$ components of the particles generated in string fragmentation on the circumference of an ellipse instead of circle originally, the calculated charged particle $v_2(\eta)$ and $v_2(p_T)$ fairly reproduce the corresponding experimental data in the Au+Au/Pb+Pb collisions at $\sqrt{s_{NN}}$=0.2/2.76 TeV. In addition, the charged particle $v_2(\eta)$ and $v_2(p_T)$ in the p+p collisions at $\sqrt s$=7 TeV as well as in the p+Au/p+Pb collisions at $\sqrt{s_{NN}}$=0.2/5.02 TeV are predicted., Comment: 7 pages, 5 figures

We calculate the real and non-statistical higher moment excitation functions ($\sqrt{s_{NN}}$ = 11.5 to 200 GeV) for the net-proton, net-baryon, and the net-charge number event distributions in the relativistic Au+Au collisions with the parton and hadron cascade model PACIAE. It turned out that because of the statistical fluctuation dominance it is very hard to see signature of the CP singularity in the real higher moment excitation functions. It is found that the property of higher moment excitation functions are significantly dependent on the window size, and hence the CP signatures may show only in a definite window for a given conserved observable non-statistical higher moments. But for a given widow size, the CP singularity may show only in the non-statistical higher moment excitation functions of a definite conserved observable., Comment: 6 pages, 4 figures

In PYTHIA6 (PYTHIA8) once the transverse momentum $p_T$ of a generated particle is randomly sampled, $p_x$ and $p_y$ are set on the circle with radius of $p_T$ randomly. This may largely suppress the development of the final hadronic state transverse momentum anisotropy from the initial state spatial asymmetry. We modify PYTHIA6.4 by randomly setting $p_x$ and $p_y$ on the circumference of an ellipse with the half major and minor axes being $p_T(1+\delta_p)$ and $p_T(1-\delta_p)$, respectively. The modified PYTHIA6.4 is then employed to systematically study the charged particle transverse momentum asymmetry in the minimum bias pp collisions at $\sqrt s$=0.9, 7, and 14 TeV. The ALICE data on the transverse sphericity as a function of charged multiplicity, $(N_{ch})$, are well reproduced with the modified PYTHIA6.4. It is found that the predicted charged particle $v_2$ upper limit is a measurable value, $\sim 0.12$, in the minimum bias pp collisions at $\sqrt s$=7 TeV. We suggest a systematic measurement for the particle transverse momentum sphericity, eccentricity (ellipticity), and elliptic flow parameter., Comment: 5 pages, 2 figures

We have used the dynamically constrained phase space coalescence model to investigate the production of light nuclei (anti-nuclei) based on the 1.134$\times 10^7$ hadronic final states generated by the PACIAE model for the 0-5% most central Au+Au collisions at $\sqrt{s_{\rm{NN}}}$=200 GeV with $|y| <$1 and $p_T<$5 acceptances. The STAR data of $\bar{_{\bar\Lambda}^ 3H}$, ${_{\Lambda}^3 H}$, $^3{\bar{He}}$, and $^3{{He}}$ yields and ratios are well reproduced by the corresponding PACIAE results. The transverse momentum distribution of $\bar{^3{He}}$ (${^3{He}}$) and $\bar{_{\bar\Lambda}^3H}$ (${_{\Lambda}^3H}$) is also given. It turned out that the transverse momentum distribution of light nuclei is close to that of the corresponding anti-nuclei., Comment: 5 pages, 2 figures

We have updated the parton and hadron cascade model PACIAE 2.0 for relativistic nuclear collisions (cf. Comput. Phys. Comm. 183(2012)333) to the new issue of PACIAE 2.1. The PACIAE model is based on PYTHIA. In the PYTHIA model, once the generated particle/parton transverse momentum $p_T$ is randomly selected, its component of $[p_x,p_y]$ was originally put on the circle with radius $p_T$ randomly. It is now replaced by put on the circumference of ellipse with half major and minor axes of $p_T(1+\delta_p)$ and $p_T(1-\delta_p)$, respectively, in order to investigate better the transverse momentum anisotropy in final hadronic state., Comment: 8 pages, 3 figures

We use the non-statistical fluctuation instead of the full one to explore the higher moment singularities of net proton event distributions in the relativistic Au+Au collisions at $\sqrt{s_{NN}}$ from 11.5 to 200 GeV calculated by the parton and hadron cascade model PACIAE. The PACIAE results of mean ($M$), variance ($\sigma^2$), skewness ($S$), and kurtosis ($\kappa$) are consistent with the corresponding STAR data. Non-statistical moments are calculated as the difference between the moments derived from real events and the ones from mixed events, which are constructed by combining particles randomly selected from different real events. An evidence of singularity at $\sqrt{s_{NN}}\sim$ 60 GeV is first seen in the energy dependent non-statistical $S$ and $S\sigma$., Comment: 5 pages,5 figures

Combining the hydrodynamic model (Hydro code) and the transport model (PACIAE model), we present the Hydro-PACIAE hybrid model. We use the Hydro-PACIAE hybrid model to calculate Au+Au collisions at $\sqrt{s_{NN}}$=130 GeV and Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV. The obtained pseudo-rapidity and transverse momentum distributions well reproduce the experimental data. This shows that the Hydro-PACIAE hybrid model is useful to describe the ultrarelativistic Heavy Ion Collisions at RHIC and LHC Energies. We used the hybrid model to calculate the elliptical flow for the Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV. The $v_2$ values are bigger than the experimental data at high $p_T$, and will become bigger when the Hydro evolution time is longer. The results indicate that the selection of the transition hypersurface has significant effect on the observable quantities., Comment: 8 pages, 8 figures

A dynamically constrained coalescence model based on the phase space quantization and classical limit method was proposed to investigate the production of light nuclei (anti-nuclei) in non-single diffractive (NSD) pp collisions at $\sqrt{s}$=7 and 14 TeV. This calculation was based on the final hadronic state in the PYTHIA and PACIAE model simulations, the event sample consisted of 1.2$\times 10^8$ events in both simulations. The PACIAE model calculated $\bar D$ yield of 6.247$\times 10^{-5}$ in NSD pp collisions at $\sqrt{s}$=7 TeV is well comparing with the ALICE rough datum of 5.456$\times 10^{-5}$. It indicated the reliability of proposed method in some extent. The yield, transverse momentum distribution, and rapidity distribution of the $\bar D$, $^3{\bar{He}}$, and $_{\bar\Lambda} ^3{\bar H}$ in NSD pp collisions at $\sqrt{s} $=7 and 14 TeV were predicted by PACIAE and PYTHIA model simulations. The yield resulted from PACIAE model simulations is larger than the one from PYTHIA model. This might reflect the role played by the parton and hadron rescatterings., Comment: 5 pages, 2 figures

Collective flow in collisions between Lead nuclei at LHC are influenced by random initial state fluctuations, especially for odd harmonics. Here we extend fluctuation studies to longitudinal fluctuations, which may have significant effect on the rapidity distribution of odd harmonics. Furthermore center of mass rapidity fluctuations are measurable, but not yet analysed. Here in the PACIAE parton and hadron molecular dynamics model we make an analysis of initial state fluctuations. As previous analyses discussed mainly the effects of fluctuations on eccentricity and the elliptic flow we pay particular attention to the fluctuations of the Center of Mass rapidity of the system, which is conservatively estimated in our model as {\Delta}y_{CM} = 0.1, by neglecting all pre-equilibrium emission effects that are increasing the y_{CM} fluctuations., Comment: 7 pages, 5 figures

We have updated the parton and hadron cascade model PACIAE for the relativistic nuclear collisions, from based on JETSET 6.4 and PYTHIA 5.7 to based on PYTHIA 6.4, and renamed as PACIAE 2.0. The main physics concerning the stages of the parton initiation, parton rescattering, hadronization, and hadron rescattering were discussed. The structures of the programs were briefly explained. In addition, some calculated examples were compared with the experimental data. It turns out that this model (program) works well., Comment: 23 pages, 7 figures

The parton and hadron cascade model PACIAE based on PYTHIA was utilized to systematically investigate the strange particle production in pp collisions at the RHIC and LHC energies. Taking the mechanism of reduction of the strange quark suppression into account the STAR and ALICE data of strange particle production in pp collisions are well reproduced. It turned out that the K/{\pi} ratio as a function of reaction energy in pp collisions shows slightly increasing from sqrt(s)=0.2 to 0.9 TeV and then turning to saturation.

The parton and hadron cascade model PACIAE based on PYTHIA was used to investigate the charged particle elliptic flow in minimum bias pp collisions at the LHC energies. The strings were distributed randomly in the transverse ellipsoid of the pp collision system with major axis of $R$ (proton radius) and minor axis of $R(1-\xi)$ before parton rescattering. The charged particle elliptic flow as a function of the random number $\xi$ and transverse momentum $p_T$ were investigated. The calculated $v_2/\epsilon$ as a function of reaction energy increases monotonously with increasing reaction energy up to $\sqrt{s}\sim$7 TeV and then turns to saturation. With the parton-parton cross section enlarges three times in parton rescattering, the rapidity integrated charged particle elliptic flow may reach 0.025 at $p_T \sim$2 GeV/c in the minimum bias pp collisions at $\sqrt{s}$=7 TeV., Comment: 7 pages, 4 figures

We have studied the centrality dependence of charged particle forward-backward multiplicity correlation strength in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV with a parton and hadron cascade model, PACIAE, based on PYTHIA. The calculated results are compared with the STAR data. The experimentally observed correlation strength characters: (1) the approximately flat pseudorapidity dependence in central collisions and (2) the monotonous decrease with decreasing centrality are well reproduced. However the theoretical results are bigger than the STAR data for the peripheral collisions. A discussion is given for the comparison among the different models and STAR data., Comment: 5pages,4figures

The elliptic flow parameter (component), $v_2$, in the Fourier expansion of event-by-event charged particle multiplicity azimuthal distribution in the momentum space is studied by taking into account the multiplicity fluctuations. The correlations between charge multiplicity and impact parameter as well as between elliptic flow parameter and impact parameter (multiplicity) are investigated by both the parton and hadron cascade model PACIAE and a multiple phase transport model AMPT. A discussion is given for the event-wise average and particle-wise average in the definition of elliptic flow parameter., Comment: 6 pages, 4 figures

The parton rescattering effect on the charged particle production in ultra-relativistic p+p collisions is studied by the parton and hadron cascade model, PACIAE, based on PYTHIA. We have calculated charged particle pseudorapidity density ($dN_{ch}/d\eta$) at mid-rapidity and the pseudorapidity distribution in inelastic and non-single diffractive p+p collisions at $\sqrt s$=200, 900, 5500, and 14000 GeV with the PYTHIA and PACIAE models. The calculated results of $\sqrt s$=900 GeV are well compared with the ALICE data. The calculated $dN_{ch}/d\eta$ as a function of center-of-mass energy well meets with the experimental data as well. Comparing the PYTHIA results (without parton rescattering) with the PACIAE results (with parton rescattering), it turned out that the parton rescattering effect plays an important role and this effect increases with increasing center-of-mass energy., Comment: 4 pages, 3 figures

The parton yield, (pseudo)rapidity distribution, and transverse momentum distribution in partonic matter assumed forming in the early stage of $pp$ and nucleus-nucleus collisions at RHIC energy ($\sqrt{s_{{NN}}}$=200 GeV) and LHC energy ($\sqrt{s_{{NN}}}$=5.5 TeV for nucleus-nucleus, 5.5 and/or 14 TeV for $pp$) are comparatively investigated with parton and hadron cascade model PACIAE. It turned out that the different parton and anti-parton spectra approach to be similar with reaction energy increasing from RHIC to LHC. We have argued that if the partonic matter forming in Au+Au collisions at RHIC energy is strongly interacting quark-gluon plasma, the one forming in Pb+Pb collisions at LHC energy might approach the real (free) quark-gluon plasma., Comment: 6 pages, 6 figures