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Liu Lianshou

Publications and source records attributed to Liu Lianshou.

At least 19 recordsLinked to original sources
arXiv2009

Model investigation on the probability of QGP formation in relativistic heavy ion collisions

The formation probability of quark-gluon plasma in relativistic heavy ion collisions for colliding nuclei of different sizes is investigated in the framework of a bond percolation model. The results show that nuclei with sizes smaller than that of Pb or Au produce QGP with probability less than unity even at very high collision energies. The dependence of the QGP-formation probability on different nuclear sizes and on various centralities of Au-Au collision are presented.

hep-ph↗
arXiv2008

The characterizing variable for critical point in momentum space

The possible experimentally observable signal in momentum space for the critical point, which is free from the contamination of statistical fluctuations, is discussed. It is shown that the higher order scaled moment of transverse momentum can serve as an appropriate signal for this point, provided the transverse momentum distribution has a sudden change when energy increases passing through the critical point. A 2-D percolation model with a linear temperature gradient is constructed to check this suggestion. A sudden change of third order scaled moment of transverse momentum is successfully observed.

nucl-th↗
arXiv2008

Pair distribution function of strongly coupled quark gluon plasma in a molecule-like aggregation model

Pair distribution function for delocalized quarks in the strongly coupled quark gluon plasma (sQGP) as well as in the states at intermediate stages of crossover from hadronic matter to sQGP are calculated using a molecule-like aggregation model. The shapes of the obtained pair distribution functions exhibit the character of liquid. The increasing correlation length in the process of crossover indicates a diminishing viscosity of the fluid system.

hep-ph↗
arXiv2008

Is there hydrodynamic flow at RHIC ?

It is argued that the observation of anisotropic azimuthal distribution of final state particles alone is insufficient to show whether the formed matter at RHIC behaves like hydrodynamic flow. Examining the intrinsic interaction (or correlation) of the formed matter should provide more definite judgement. To the end, a spatial-dependent azimuthal multiplicity-correlation pattern is suggested. It shows clearly in the pattern that there are two kinds of interactions at the early stage of Au + Au collisions at $\sqnn=200$ GeV generated by RQMD with hadron re-scattering and AMPT with string melting. This is out of the expectation from the elliptic flow driven by anisotropic expansion.

nucl-th↗
arXiv2007

Examining the crossover from hadronic to partonic phase in QCD

It is argued that, due to the existence of two vacua -- perturbative and physical -- in QCD, the mechanism for the crossover from hadronic to partonic phase is hard to construct. The challenge is: how to realize the transition between the two vacua during the gradual crossover of the two phases. A possible solution of this problem is proposed and a mechanism for crossover, consistent with the principle of QCD, is constructed. The essence of this mechanism is the appearance and growing up of a kind of grape-shape perturbative vacuum inside the physical one. A dynamical percolation model based on a simple dynamics for the delocalization of partons is constructed to exhibit this mechanism. The crossover from hadronic matter to sQGP as well as the transition from sQGP to wQGP in the increasing of temperature is successfully described by using this model with a temperature dependent parameter.

hep-th↗
arXiv2006

A Monte Carlo study on the production scale and internal structure of jets in high energy collisions

The production scale and internal structure of jets produced in high energy collisions are studied using Jetset7.4 and Herwig5.9 Monte Carlo generators. Two scales are found. One is the jet-development scale, which determines the size of the jet developed from a mother-parton. The other one is the jet-production scale, the jets produced with this scale are the most consistent with QCD jet-production dynamics and will provide the most reliable dynamical information about their mother-partons.

hep-ph↗
arXiv2006

A Monte Carlo Study on the Identification of Quark-gluon Fusion Product in QCD-instanton Induced Processes in Deep-inelastic Scattering

Different methods to reconstruct the quark-gluon fusion product and current jet are tried in deep-inelastic e-p scattering events with instanton as background generated by QCDINS Monte Carlo code. A comparison of these methods are performed and a good method is found which can reconstruct well the energies of current jet and instanton product as well as the mass of the latter. The isotropy property of the instanton product and jet are calculated and compared. A parameter characterizing the degree of ``hardness'' of the instanton product is presented.

hep-ph↗
arXiv2006

An inversion-asymmetric source function for HBT analysis in relativistic heavy ion collisions

The inversion-asymmetry of the emission source in relativistic heavy ion collision under the Bertsch-Pratt convention is discussed and explicitly exhibited by a Monte Carlo model. The Gaussian source function popularly used in the HBT analysis of relativistic heavy ion collisions is invalid in this case. An inversion-asymmetric source function is suggested. A method for extracting the inversion-asymmetry degree of the source together with the source size from experimental data is proposed.

nucl-th↗
arXiv2006

The Narrowing of Charge Balance Function and Hadronization Time in Relativistic Heavy Ion Collisions

The widths of charge balance function in high energy hadron-hadron and relativistic heavy ion collisions are studied using the Monte Carlo generators PYTHIA and AMPT, respectively. The narrowing of balance function as the increase of multiplicity is found in both cases. The mean parton-freeze-out time of a heavy-ion-collision event is used as the characteristic hadronization time of the event. It turns out that for a fixed multiplicity interval the width of balance function is consistent with being independent of hadronization time.

nucl-th↗
arXiv2006

An Empirical Study of Boosted Neural Network for Particle Classification in High Energy Collisions

The possible application of boosted neural network to particle classification in high energy physics is discussed. A two-dimensional toy model, where the boundary between signal and background is irregular but not overlapping, is constructed to show how boosting technique works with neural network. It is found that boosted neural network not only decreases the error rate of classification significantly but also increases the efficiency and signal-background ratio. Besides, boosted neural network can avoid the disadvantage aspects of single neural network design. The boosted neural network is also applied to the classification of quark- and gluon- jet samples from Monte Carlo \EE collisions, where the two samples show significant overlapping. The performance of boosting technique for the two different boundary cases -- with and without overlapping is discussed.

hep-ph↗
arXiv2006

Effect of equilibrium phase transition on multiphase transport in relativistic heavy ion collisions

The hadronization scheme for parton transport in relativistic heavy ion collisions is considered in detail. It is pointed out that the traditional scheme for particles being freezed out one by one leads to serious problem on unreasonable long lifetime for partons. A super-cooling of the parton system followed by a collective phase transition is implemented in a simple way. It turns out that the modified model with a global phase transition is able to reproduce the experimental longitudinal distributions of final state particles better than the original one does. The encouraging results indicate that a relevant parton transport model for relativistic heavy ion collision should take equilibrium phase transition into proper account.

nucl-th↗
arXiv2004

Charge Fluctuations in $π^{+}\rp$ and $\rK^{+}\rp$ Collisions at 250 GeV/$c$

We report on measurements of event-by-event charge fluctuations in $π^{+}\rp$ and $\rK^{+}\rp$ collisions at 250 GeV/$c$. The dependence of these fluctuations on the size of the rapidity windows are presented for the first time in the full phase space domain. The corrections for the influence of global charge conservation and leading-particle stopping are tested by the data. The discrepancy due to incomplete correction given by STAR and PHENIX are estimated. The dependence of the fluctuations on the position of the rapidity bin and on the multiplicity at different rapidity windows are also presented.

hep-ex↗
arXiv2004

A Comparison of different measures for dynamical event-mean transverse momentum fluctuation

Various measures for the dynamical event-mean transverse momentum fluctuation are compared with the real dynamical fluctuation using a Monte Carlo model. The variance calculated from the G-moments can reproduce the dynamical variance well, while those obtained through subtraction procedures are approximate measures for not very low multiplicity. The Phi_pt can also serve as an approximate measure after divided by the square root of mean multiplicity.

hep-ph↗
arXiv2002

A Monte Carlo Study of the Levy Stability and Multifractal Spectrum in e+e- collisions

The Levy stability analysis is carried out for e+e- collisions at Z^0 mass using Monte Carlo method. The Levy index μis found to be μ=1.701 +- 0.043. The self-similar generalized dimensions D(q) and multi-fractal spectrum f(α) are presented. The Renyi dimension D(q) decreases with increasing q. The self-similar multi-fractal spectrum is a convex curve with a maximum at q = 0, α= 1.169 +- 0.011. The right-side part of the spectrum, corresponding to negative values of q is obtained through analytical continuation.

hep-ph↗
arXiv2002

On the Phase Space Partition in High Energy Collisions

In high energy hadron-hadron and e+e- collisions, to isolate a part of the phase space in multi-hadron final states is necessary for exploring the underlying dynamics. It is shown that the partition of phase space according to the value of rapidity, popularly used in hadron-hadron collisions, is inappropriate for the study of e+e- collisions. The proper way in the latter case is to identify the visible jets and take them as objects for detailed study, forming an extended phase space. The value y_cut^(0) of the distance-measure for the identification of visible jets is determined. A new variable $r$ is introduced to further partition the phase space inside jets, which possesses a very good anomalous scaling property, showing that the $r$-distribution inside jets is a self-similar fractal.

hep-ph↗
arXiv2002

A Monte Carlo Study on the Dynamical Fluctuations Inside Quark and Antiquark Jets

The dynamical fluctuations inside the quark and antiquark jets are studied using Monte Carlo method. Quark and antiquark jets are identified from the 2-jet events in e+e- collisions at 91.2 GeV by checking them at parton level. It is found that transition point exists inside both of these two kinds of jets. At this point the jets are circular in the transverse plane with respect to the property of dynamical fluctuations. The results are consistent with the fact that the third jet (gluon jet) was historically first discovered in e+e- collisions in the energy region 17-30 GeV.

hep-ph↗