1994 Vol. 18, No. 9

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Application of Neural Network in τ→ρVτ Polarization Analysis
Zhang Ziping, Wang Yifang
1994, 18(9): 769-777.
An artificial neural network was built to select events in the τ→ρVτ polarization analysis at LEP/L3, much better selection efficiency has been achieved.Detailed studies show that no systematic errors or bias have been introduced by the application of neural network. A polarization of Pτ=-0.129±0.050±0.050 for this channel was obtained by using a sample of 8977 τ+τ pairs collected near the peak of Z0 resonance. The neural network training method and some details are described.
Poisson-Like Shape and Shoulder Structure of Hadron Multiplicity Distributions in e+e Annihilation at Z0 Energy Region
Xie Yigang, Chai Yong
1994, 18(9): 778-787.
The charged multiplicity distributions of hadron final states in the e+e annihilation at the 91.2 GeV Z0 energy region are fitted with Poisson shape in different rapidity windows for double and single hemisphere. The multiplicities which are in Poisson-like shapes can be got according to the parameter /D and fitting qualities are compared with the results derived from the relevant theoretical models.The relationship between the Poisson-like shape and KNO scaling is discussed. The connection between the parameters expressing the deviation from the Poisson shape and non-independent particle emission and multiplicity correlation strength is analyzed. The "shoulder structure" is observed in the central rapidity region and analyzed with multi-jets by using the JADE jet analysis algorithm.
The Study of Meteorological Effects on TeV Cosmic Ray Flux
Jia Huanyu, Cao Zhen, Zhang Huimin
1994, 18(9): 788-793.
The possibility for monitoring TeV cosmic ray flux with China-Japan joint Tibet Air Shower Array (ASA) is discussed. The meteorological influences on trigger rate of ASA are analysed. A correction method for these effects is found and is adopted in the data correction.
Fitting Method and Error Study for Tau Lifetime Measurements of L3 Experiment
Yang Changgen, Chen Hesheng, Jin Bingnian, Tang Xiaowei
1994, 18(9): 794-799.
The sign-flip probability of the impact parameter in the measurement of the tau lifetime is studied. The probability of the impact parameter with the negative value is introduced into the formula to fit the tau lifetime in the L3 experiment.The systematic errors of the drift velocity and grid time calibration are also studied by using the special designed L3 Time Expansion Chamber (TEC).
Study of Collective Flow for 64Zn+27Al, Collisions at 57 MeV/u
He Zhiyong1, J.Peter2, J.C.Angelique2, G.Bizard2, R.Brou2, D.Cussol2, A.Kerambrun2, J.P.Patry2, R.Regimbart2, J.C.Steckmeyerr2, B.Tamain2, E.Vient2, G.Auger3, C.Cabot<sup
1994, 18(9): 800-806.
The collective matter flow in the 64Zn-27Al reaction at 57MeV/u is measured in terms of a 4πcharged particle array. The events as a function of the impact parameter are sorted by using the average parallel velocity method. The reaction plane is determined by means of the transverse momentum analysis method. It is observed that the collective transverse momentum in the reaction plane (sideward flow parameter) varys with the impact parameter and producted particles.
Production Percentages of L=1 Excited Baryons in e+e Annihilation
Wang Qun, Xie Qubing
1994, 18(9): 807-812.
We use a simple decay model of low excited baryon states to evaluate the decay contributions of these states to the (1/2)+ and (3/2)+ baryons. we further input the experiment values R1=(1530)/Ξ, R2=∑(1385 )/∑and R3=∧(1520)/∑(1385)at γ on c.m. energy and use the basic relations derived in the precious paper todetermine the total production rates of the low excited baryons of various SUf(3)multiplets.
Three-Dimensional Exactly Solvable Model With Cubic Lattice
Hu Zhanning
1994, 18(9): 813-820.
The weight function Sk of Baxter-Bazhanov model is discussed in detail and a complete proof of the three-dimensional star-star relation is obtained.
Dimensional Regularization and π-meson Properties in Nambu-Jona-Lasinio Model
Zhang Jianwei, Deng Weizhen, Yang Zesen, Yang Liming
1994, 18(9): 821-828.
The dimensional regularization approach in the operator representation of the Dirac algebra defined in the extended Grassmann space is applied to investigate the properties of the π-meson mode in the Nambu-Jona-Lasinio model. It is shown that the analytic formula for hadronic modes in the Nambu-Jona-Lasinio model as well as the numerical results which fit the experimental data can be obtained by employing this method.
Difference of Particle Multiplicities Between Quark Jets of Different Flavors in e+e Annihilation
Liu Ximing
1994, 18(9): 829-835.
The changed particle multiplicity of heavy quark jet events in e+e annihilation is calculated by the quark production rule and quark combination rule. The results agree well with experiments. The comparison of the charged particle multiplicities with the light quark jet and average quark jet is presented.
Symmetry for Semileptonic Decays of B-Baryons
Hou Yunzhi
1994, 18(9): 836-841.
We have discussed the nonleptonic decay of charmless b-flavored baryons in the previous article. By using US(3)f flavor symmetry, the semileptonic decays of bottom baryons are further studied. Some decay rates and relations are obtained.We hope that in the near future, the experimental data on these decays will beavailable so that the test on the standard model will be provided.
The Relationship Between the Energy Storage and the Entrance Channel Dynamics in HIC
Zeng Xianghua, Ge Lingxiao, Zuo Wei
1994, 18(9): 842-847.
The relationship between the energy storage and the entrance channel dynamics (i.e. incident energy, impact parameter and collision system) is studied by using the BUU model. The effects of the entrance channel mass asymmetries on theexcitation energy of the compound systems are also discussed.
Preequilibrium Neutron Emissions from Nucleus-Nucleus Collisions in Fermi Domain
Wang Zhisong, Huo Yukun
1994, 18(9): 848-852.
Preequilibrium neutron emissions from nucleus-nucleus collisions 36Ar+108Ag (35MeV/u) and 14N+108Ag (35MeV/u) are simulated in the BUU model. Thesimulations are in agreement with the intermediate rapidity source (IRS) parts in the moving source fit approach, which indicates that the IRS parts come from the very early stage of collisions, and are equivalent to preequilibrium emissions. The time interval of the preequilibrium neutron emission process is studied in terms ofnucleon-nucleon collisions.
Isospin Effects on Dynamics of Heavy Ion Collisions
Zhu Quanling, Ge Lingxiao, Zhang Xiaodong
1994, 18(9): 853-857.
The interaction terms of the isospin-dependent symmetric energy and Coulomb energy are considered in the quantum molecular dynamics. The effects of thesymmetric energy on the mass distribution and cluster formation in the head oncollisions of the systems 20Ne+20Ne and 28Ne+20Ne at the incident energy of 30MeV/u are discussed, and the favorable condition for synthesizing neutron-rich isotopes is predicted.
The Refinement of α Model and the Analytical Calculation of Levy Exponent
Lin Hai, Zhang Yang, Liu Lianshou
1994, 18(9): 858-864.
In order to investigate the intermittency behaviour in high energy collisions using the Levy stability theory, it is necessary to develop a method for the analytical calculation of Levy exponent. In view of this, the random cascading αmodel is refined to make the expression of the probability ω of elementary division linear.Using this model, the Levy exponent is calculated analytically. The results are consistent with the theoretical prediction. The analytical expression for the moments of ω is obtained. In order to compare the present model with the original one, the MC simulation is done for both models, and the intermittency indices are calculated,showing that both models are practical and reliable.