arXiv subjects

Liu Lianshou

Publications and source records attributed to Liu Lianshou.

At least 37 records · Page 2Linked to original sources

arXiv2001

A Monte Carlo Study on the Identification of Quark and Gluon Jets

Three jets events in the e$^+$e$^-$ collisions at 91.2 GeV are investigated using both HERWIG and JETSET Monte Carlo generators. The angles between the three jets are used to identify the quark and gluon jets. The analysis at parton level is done to ensure the reasonableness of this method and an angular cut is ultilized to improve the purity of this identification. The multiplicity inside the identified quark or gluon jets agree with the QCD predictions.

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arXiv2001

A Monte Carlo Study of Erraticity Behavior in Nucleus-Nucleus Collisions at High Energies

It is demonstrated using Monte Carlo simulation that in different nucleus$-$nucleus collision samples, the increase of the fluctuation of event factorial moments with decreasing phase space scale, called erraticity, is still dominated by the statistical fluctuations. This result does not depend on the Monte Carlo models. Nor does it depend on the concrete conditions, e.g. the collision energy, the mass of colliding nuclei, the cut of phase space, etc.. This means that the erraticity method is sensitive to the appearance of novel physics in the central collisions of heavy nuclei.

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arXiv2001

On the Scale of Visible Jets in High Energy Electron-Positron Collisions

A study of the dynamical fluctuation property of jets is carried out using the Monte Carlo method. The results suggest that, the anisotropy of dynamical fluctuations in the hadronic system inside jets, changes abruptly with the variation of the cut parameter y_cut. A transition point exists, where these fluctuations behave like those in soft hadronic collisions, i.e. being circular in the transverse plane with respect to dynamical fluctuations.

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arXiv2000

A Monte Carlo Study of the Dynamical-Flucautation Property of the Hadronic System Inside Jets

A study of the dynamical fluctuation property of jets is carried out using Monte Carlo method. The results suggest that, unlike the average properties of the hadronic system inside jets, the anisotropy of dynamical fluctuations in these systems changes abruptly with the variation of the cut parameter $\yct$. A transition point exists, where the dynamical fluctuations in the hadronic system inside jet behave like those in soft hadronic collisions, i.e. being circular in the transverse plan with repect to dynamical fluctuations. This finding obtained from Jetset and Herwig Monte Carlo is encouraged to be checked by experiments.

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arXiv2000

Thermal Equilibration and Ellipsoidal Expansion of Rotationally-Symmetrical Longitudinal Flow in Relativistc Heavy Ion Collisions

A rotationally-symmetrical ellipsoidal flow model is proposed for the relativistic heavy-ion collisions and compared with the 14.6 A GeV/c Si-Al and 10.8 A GeV/c Au-Au collision data. The large stopping in the heavier collision system and heavier produced particles is accounted for by using the ellipsoidal flow picture. The central dip in the proton and deuteron rapidity distributions for Si-Al collision are reproduced.

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arXiv2000

The Influence of Multiplicity Fluctuation on the Erraticity Behaviour in High Energy Collisions

The influence of multiplicity distribution (fluctuation of multiplicity in the event space) on the erraticity behaviour in high energy collisions is investigated via Monte Carlo simulation and compared with the experimental results from NA27 data. It is shown that, the erraticity phenomenon is insensitive to the multiplicity fluctuation. When the average multiplicity is low, this phenomenon is dominated by the statistical fluctuations also in the case of multiplicities, fluctuating from event to event.

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arXiv1999

The Influence of Multiplicity Distribution on the Erraticity Behavior of Multiparticle Production

The origin of the erraticity behaviour observed recently in the experiment is studied in some detail. The negative-binomial distribution is used to fit the experimental multiplicity distribution. It is shown that, with the multiplicity distribution taken into account, the experimentally observed erraticity behaviour can be well reproduced using a flat probability distribution. The dependence of erraticity behaviour on the width of multiplicity distribution is studied.

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arXiv1999

Identification of Colour Reconnection using Factorial Correlator

A new signal is proposed for the colour reconnection in the hadronic decay of W+ W- in e+e- collisions. Using Pythia Monte Carlo it is shown that this signal, being based on the factorial correlator, is more sensitive than the ones using only averaged quantities.

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arXiv1999

Model Investigation of Non-Thermal Phase Transition in High Energy Collisions

The Non-thermal phase transition in high energy collisions is studied in some detail in the framework of random cascade model. The relation between the characteristic parameter $λ_q$ of phase transition and the rank $q$ of moment is obtained using Monte Carlo simulation, and the existence of two phases in self-similarly cascading multiparticle systems is shown. The relation between the critical point $q_c$ of phase transition on the fluctuation parameter $α$ is obtained and compared with the experimental results from NA22. The same study is carried out also by analytical calculation under central limit approximation. The range of validity of the central limit approximation is discussed.

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arXiv1999

The Influence of Statistical Fluctuations on Erraticity Behavior of Multiparticle System

It is demonstrated that in low multiplicity sample, the increase of the fluctuation of event-factorial-moments with the diminishing of phase space scale, called ``erraticity'', are dominated by the statistical fluctuations. The erraticity behavior observed at NA27 experiment can be readily reproduced by pure statistical fluctuations. Applying erraticity analysis to a high multiplicity sample is recommended and the method is improved at very high multiplicity case as well.

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arXiv1999

On the Dominance of Statistical Fluctuation in the Factorial-Moment Study of Chaos in Low Multiplicity Events of High Energy Collisions

It is shown using Monte Carlo simulation that for low multiplicity events the single-event factorial moments are saturated by the statistical fluctuations. The diverse of the event-space moments $C_{p,q}$ of single-event moments with the diminishing of phase space scale, called ``erraticity'', observed in experiment can readily be reproduced by a flat probability distribution with only statistical fluctuations and therefore does not indicate the existence of chaos as suggested. The possibility of studying chaos in high multiplicity events using erraticity analysis is discussed.

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arXiv1998

On the Factorial Moment Analysis of High Energy Experimental Data with Non-integer Partition Number

It is pointed out that in doing the factorial moment analysis with non-integer partition $M$ of phase space, the influence of the phase-space variation of two- (or more-) particle correlations has to be considered carefully. In this paper this problem is studied and a systematic method is developed to minimize this influence. The efficiency and self-consistency of this method are shown using the data of 250 GeV/$c$ $π^+$p and K$^+$p collisions from the NA22 experiment as example.

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arXiv1998

Levy Stability Index from Multifractal Spectrum

A method for extracting the Levy stability index $μ$ from the multi-fractal spectrum $f(α)$ in high energy multiparticle production is proposed. This index is an important parameter, characterizing the non-linear behaviour of dynamical fluctuations in high energy collisions. Using the random cascading $α$ model as example, the validity of this method is tested. It is shown that this method, basing on a linear fit, is consistent with and more accurate than the usual method of fitting the ratio of $q$th to 2nd order multi-fractal (Rényi) dimensions to the Peschanski formula.

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arXiv1998

On a Qualitative Difference between the Dynamics of Particle Production in Soft and Hard Processes of High Energy Collisions

The qualitative difference between the anomalous scaling properties of hadronic final states in soft and hard processes of high energy collisions is studied in some detail. It is pointed out that the experimental data of e^+e^- collisions at $E_{cm}=$91.2 GeV from DELPHI indicate that the dynamical fluctuations in e^+e^- collisions are isotropical, in contrast to the anisotropical fluctuations oberserved in hadron-hadron collision experiments. This assertion is confirmed by the Monte Carlo simulation using the Jetset7.4 event generator.

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arXiv1998

Scaling Exponent and Fluctuation Strength in High Energy Collisions

The information on dynamical fluctuations that can be extracted from the anomalous scaling observed recently in hadron-hadron collision experiments is discussed in some detail. A parameter ``effective fluctuation strength'' is proposed to estimate the strength of dynamical fluctuations. The method for extracting its value from the experimentally observed quantities is given. Some examples for the application of this method to real experimental data are presented.

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arXiv1998

An Algorithm for Selecting QGP Candidate Events from Relativistic Heavy Ion Collision Data

The formation of quark-gluon plasma (QGP) in relativistic heavy ion collision, is expected to be accompanied by a background of ordinary collision events without phase transition. In this short note an algorithm is proposed to select the QGP candidate events from the whole event sample. This algorithm is based on a simple geometrical consideration together with some ordinary QGP signal, e.g. the increasing of $K/π$ ratio. The efficiency of this algorithm in raising the 'signal/noise ratio' of QGP events in the selected sub-sample is shown explicitly by using Monte-Carlo simulation.

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arXiv1998

The Contribution of Reggeon in Charge Exchange Processes

We discuss in this paper The experimental results on maximum psedo-rapidity $η_{max}$ distribution in the charge exchange process $e+p\to e+n+X$ in ZEUS Collaboration at HERA. We calculate the contributions of \regg ($ρ$-Reggeon associated with $ρ$ meson) from regge phenomenology and $π^{+}$-exchange from pion cloud model. The results show that neither the \regg-exchange nor the pion cloud model alone can explain the experimental data well, but after considering both these two processes together, by using Monte Carlo simulation, a good agreement between theoretical results and experimental data is found. This means that in discussing the large rapidity gap phenomena in deep inelastic scattering, both of the two processes play substantial role.

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arXiv1996

On the Influence of Momentum Conservation upon the Scaling Behaviour of Factorial Moments in High Energy Multiparticle Production

The experimental results on the falling down of scaled factorial moments in azimuthal variable $ϕ$ is studied in some detail. It is shown that this phenomenon may be referred to the influence of transverse momentum conservation. The existing experimental data from DELPHI, EMU08, NA22 and UA1 are successfully explained. Various methods are proposed to partly eliminate this influence and rule out the 'falling down' of factorial moments.

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