1994 Vol. 18, No. 9
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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.
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
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.
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).
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.
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.
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.
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.
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.
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 (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 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.
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.
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.
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