arXiv subjects

Dai-Mei Zhou

Publications and source records attributed to Dai-Mei Zhou.

66 records · Page 4Linked to original sources

arXiv2009

Exploring behaviors of partonic matter forming in early stage of $pp$ and nucleus-nucleus collisions at ultra-relativistic energies

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.

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arXiv2008

PACIAE Model Predictions for Pb+Pb Collisions at LHC Compared to the Au+Au Collisions at RHIC

The parton and hadron cascade model PACIAE is used to simulate the 0-6, 15-25, and 35-45 % most central Au+Au collisions at \sqrt{s_{NN}}=19.6, 62.4, 130, and 200 GeV and the 0-10 % most central Pb+Pb collisions at \sqrt{s_{NN}}=5500 GeV. The calculated charged multiplicity and the charged particle transverse momentum distribution, pseudorapidity distribution, and extended longitudinal scaling for Au+Au collisions well agree with the corresponding PHOBOS data. Thus the above observables calculated for Pb+Pb collisions would be a reliable prediction.

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arXiv2008

Theoretical analysis for the apparent discrepancy between pbarp and pp data in charged particle forward-backward multiplicity correlations

The strength of charged particle forward-backward multiplicity correlation in pbar+p and p+p collisions at s^1/2 = 200 GeV is studied by PYTHIA 6.4 and compared to the UA5 and STAR data correspondingly. It is turned out that a factor of 3-4 apparent discrepancy between UA5 and STAR data can be attributed to the differences in detector acceptances and observing bin interval in both experiments. A mixed event method is introduced and used to calculate the statistical correlation strength and the dynamical correlation strengths stemming from the charge conservation, four- momentum conservation, and decay, respectively. It seems that the statistical correlation is much larger than dynamical one and the charge conservation, four-momentum conservation and decay may account for most part of the dynamical correlation. In addition, we have also calculated the correlation strength by fitting the charged particle multiplicity distribution from PYTHIA to the Negative Binomial Distribution and found that the result agrees well with the correlation strength calculated by mixed events.

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arXiv2006

Kinetic Description of a Finite Temperature Meson Gas

A transport model based on the mean free path approach for an interacting meson system at finite temperatures is discussed. A transition to a quark gluon plasma is included within the framework of the bag model. We discuss some calculations for a pure meson gas where the Hagedorn limiting temperature is reproduced when including the experimentally observed resonances. Next we include the possibility for a QGP formation based on the MIT bag model. The results obtained compare very well with Lattice QCD calculations. In particular the cross over to the QGP at about 175 MeV temperature is nicely reproduced.

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arXiv2006

Discrepancy between hadron matter and quark-gluon matter in net charge transfer fluctuation

A parton and hadron cascade model, PACIAE, is employed to investigate the net charge transfer fluctuation within $|η|$=1 in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. It is turned out that the observable of net charge transfer fluctuation, $κ$, in hadronic final state (HM) is nearly a factor of 3 to 5 larger than that in initial partonic state (QGM). However, only twenty percent of the net charge transfer fluctuation in the QGM can survive the hadronization

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arXiv2005

A Novel Dynamical Approach To Relativistic Heavy Ion Collisions

A transport model for ultra-relativistic nucleus-nucleus collisions based on the mean free path approach is proposed. The method is manifestly Lorentz invariant. We discuss some calculations for pp and AA collisions and compare to a previously proposed transport model and to data. We demonstrate that our approach gives a different impact parameter distribution already in pp collisions as compared to the previous one. The role of hadronization times is discussed. Comparison to data is reasonable and the model can be easily modified to take into account genuine many body effects and quantum statistics similarly to low energy heavy ion collisions.

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arXiv2003

Limiting fragmentation and $ϕ$ meson production at RHIC

The PHOBOS's limiting fragmentation etc. three empirical scaling rules for charged multiplicity in $Au+Au$ collisions at RHIC are investigated by a hadron and string cascade model LUCIAE. Similar studies are performed for the $ϕ$ meson exploring its production mechanism via comparing with the charged multiplicity. The LUCIAE results for charged multiplicity are compatible with PHOBOS observations. However, for the $ϕ$ meson the three empirical scaling rules are either kept only or kept better in the LUCIAE calculations without reduction mechanism of the $s$ quark suppression extra introduced for the strangeness in LUCIAE model. These results seem indicating a universal production mechanism for charged particle and $ϕ$ meson in string fragmentation regime. It is discussed that the PHOBOS's empirical scaling rules are model dependent indeed.

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arXiv2003

Net charge fluctuation and string fragmentation

We present simulation results of net charge fluctuation in $Au+Au$ collisions at $\sqrt{s_{nn}}$=130 GeV from a dynamic model, JPCIAE. The calculations are done for the quark-gluon phase before hadronization, the pion gas, the resonance pion gas from $ρ$ and $ω$ decays and so on. The simulations of the charge fluctuation show that the discrepancy exists between the dynamic model and the thermal model for a pion gas and a resonance pion gas from $ρ$ and $ω$ decays while the simulated charge fluctuation of the quark-gluon phase is close to the thermal model prediction. JPCIAE results of net charge fluctuation in the hardonic phase are nearly 4-5 times larger than one for the quark-gluon phase, which implies that the charge fluctuation in the quark-gluon phase may not survive the hadronization (string fragmentation) as implemented in JPCIAE.

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arXiv2002

Behavior of the charge fluctuation in relativistic nucleus-nucleus collisions

Using a hadron and string cascade model, JPCIAE, we investigated the dependence of event-by-event charge fluctuation on the energy, centrality, window size, resonance decay, and the final state interaction for $Pb+Pb$ collisions at SPS and LHC energies and $Au+Au$ collisions at RHIC energies. The JPCIAE results of charge fluctuation as a function of the rapidity window size in $Pb+Pb$ collisions at SPS energies were compared with the preliminary NA49 data. Comparisons with STAR and PHENIX data of $Au+Au$ collisions at $\sqrt{s_{nn}}$=130 GeV were also given. It seems that the final state interaction and resonance decay play a gentle role on the charge fluctuations. The charge fluctuations are slightly decreasing with or nearly independent of the reaction energy and hardly depend on the collision centrality.

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arXiv2002

Energy dependence of string fragmentation function and $ϕ$ meson production

The $ϕ$ meson productions in $Au+Au$ and/or $Pb+Pb$ collisions at AGS, SPS, RHIC, and LHC energies have been studied systematically with a hadron and string cascade model LUCIAE. After considering the energy dependence of the model parameter $α$ in string fragmentation function and adjusting it to the experimental data of charged multiplicity to a certain extent, the model predictions for $ϕ$ meson yield, rapidity, and/or transverse mass distributions are compatible with the experimental data at AGS, SPS and RHIC energies. A calculation for $Pb+Pb$ collisions at LHC energy is given as well. The obtained fractional variable in string fragmentation function shows a saturation in energy dependence. It is discussed that the saturation of fractional variable in string fragmentation function might be a qualitative representation of the energy dependence of nuclear transparency.

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arXiv2002

Charged multiplicity density and number of participant nucleons in relativistic nuclear collisions

The energy and centrality dependences of charged particle pseudorapidity density in relativistic nuclear collisions were studied using a hadron and string cascade model, JPCIAE. Both the relativistic $p+\bar p$ experimental data and the PHOBOS and PHENIX $Au+Au$ data at RHIC energy could be fairly reproduced within the framework of JPCIAE model and without retuning the model parameters. The predictions for $Pb+Pb$ collisions at the LHC energy were also given. We computed the participant nucleon distributions using different methods. It was found that the number of participant nucleons is not a well defined variable both experimentally and theoretically. Thus it may be inappropriate to use the charged particle pseudorapidity density per participant pair as a function of the number of participant nucleons for distinguishing various theoretical models. A discussion for the effect of different definitions in nuclear radius (diffused or sharp) was given.

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arXiv2001

Energy and centrality dependences of charged multiplicity density in relativistic nuclear collisions

Using a hadron and string cascade model, JPCIAE, the energy and centrality dependences of charged particle pseudorapidity density in relativistic nuclear collisions were studied. Within the framework of this model, both the relativistic $p+\bar p$ experimental data and the PHOBOS and PHENIX $Au+Au$ data at $\sqrt s_{nn}$=130 GeV could be reproduced fairly well without retuning the model parameters. The predictions for full RHIC energy $Au+Au$ collisions and for $Pb+Pb$ collisions at the ALICE energy were given. Participant nucleon distributions were calculated based on different methods. It was found that the number of participant nucleons, $ $, is not a well defined variable both experimentally and theoretically. Therefore, it is inappropriate to use charged particle pseudorapidity density per participant pair as a function of $ $ for distinguishing various theoretical models.

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