1994 Vol. 18, No. S3

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Improvements of the L3 TEC Track Resolution of Vertex
Yang Changgen, Chen Hesheng, Jin Bingnian, Tang Xiaowei, M. Pohl
1994, 18(S3): 215-222.
Two methods are used to improve the L3 TEC track resolution at vertex. First, refit the lepton tracks by constrained curvature from high precision measurements on electron energy and muon moments. Second, correct the average value of track offsets in each half-sector of TEC. Combined methods improve the lepton track resolution at vertex from 137 μm to 60 μm.
Poisson-Like Shape and Shoulder Structure of Hadron Multiplicity Distributions in e+e- Annihilation at Z0 Energy
Xie Yigang, Cai Yong
1994, 18(S3): 223-234.
The charged multiplicity distributions of final state hadrons in the e+e- annihilation at 91.2 GkV Z0 energy region are fitted with Poisson shape in different rapidity windows for full-jets and double jets events in double and single hemisphere. The multiplicity distributions which are in Poisson-like shape are obtained according to the parameter <n>/D and the fitting quality, and are compared with the results derived from the relevant theoretical models. The relationship between 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, as well as multiplicity correlation strength is analyzed. The "shoulder structure" is observed in single hemisphere for central rapidity region and analyzed by using the JADE jet analysis algorithm.
Meteorological Effects on the Trigger Rate of Air Showers Observed with the Tibet Air Shower Array
Jia Huanyu, Cao Zhen, Zhang Huimin
1994, 18(S3): 235-242.
A possibility of monitoring a few TeV cosmic ray flux with China-Japan joint Tibet Air Shower Array is discussed. The meteorological effects are examined using the data obtained with this array, and a correction of these effects on the data is discussed.
Fitting Method and Error Study for Tau Lifetime Measurement of L3 Experiment
Yang Changgen, Chen Hesheng, Jin Bingnian, Tang Xiaowei, M. Pohi
1994, 18(S3): 243-250.
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 on the lifetime are also studied by using the special designed L3 Time Expansion Chamber (TEC).
Radioactive Ion Beams at HIRFL
Zhan Wenlong, Guo Zhongyan, Zhou Jianqun, Yin Quanmin, Zhao Youxiong, Wang Jinchuan, Xi Hongfei, Wang Yifang, Luo Yongfeng
1994, 18(S3): 251-258.
At the first stage the Radioactive Ions Beam Line in Lanzhou (RIBLL) is a Projectile Fragmentation (PF)-type Radioactive Nuclide Beam (RNB) facility, in which neutron-rich and proton-rich RNB are produced by means of the energetic projectile fragmentation at around 0°. The mechanisms of RNB production, separation, transportation and identification are introduced; the structure and characteristics of this system are described. The results of test run are also reported in this paper.
The Stochastic Quark Combination Mechanism and the Production of Excited Baryons in e+e- Annihilations
Wang Qun, Xie Qubing
1994, 18(S3): 259-264.
Two relations for the production weights of baryons including all their excited states are derived based on the properties of hadronization in the stochastic quark combination scheme. The so-called Mspin suppression" and why singlet baryons have high production rates are naturally explained. Approaches and conditions to extract the production percentages of excited baryons are discussed.
Canonical Symmetry in a System with Singular Lagrangian and Ward Identities
Li Ziping
1994, 18(S3): 265-274.
An algorithm to construct the generator of gauge transformation for a constrained Hamiltonian system is given. The relation among the coefficients connected with first-class constraints in the generator are cleared. Based on the generating functional in the phase space, the corresponding Ward identities in the canonical formalism are deduced. An application of above results to a model in field theory which is equivalent to the mixed Chern-Simons Lagrangian is discussed in detail.
Refinement of α-Model and Analytical Calculation of Levy Index
Lin Hai, Zhang Yang, Liu Lianshou
1994, 18(S3): 275-282.
In order to investigate the intermittency behavior in high energy collision using the Levy stable theory, it is necessary to develop a method for the analytical calculation of Levy index. In view of this, the random cascading a-model is refined to make the expression of the probability ω of elementary division linear. The Levy index is calculated analytically in this revised model and 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 with both models, and the intermittency indices are calculated, showing that both models are practical and reliable.
The Production Percentages of L=1 Baryons in e+e- Annihilation
Wang Qun, Xie Qubing
1994, 18(S3): 283-290.
We use a simple decay model for the lowest excited baryons to evaluate their decay contributions to the ground states. We further input the experimental data R1=Ξ(1530)/Ξ, R2=Σ(1385)/Σ(1385) and R3=λ(1520)/Σ(1385) at γ(1S) resonance and use the basic relations derived in the previous paper to determine the total production rates of the lowest excited baryons of various SUf(3) multiplets.
Three-Dimensional Exactly Solvable Model with Cubic Lattice
Hu Zhanning
1994, 18(S3): 291-300.
The weight function Sk of the Baxter-Bazhanov model is discussed in detail, and a complete proof of the three dimensional star-star relation is presented.
Isospin Effects on Dynamics of Heavy Ion Collisions
Zhu Quanling, Ge Lingxiao, Zhang Xiaodong
1994, 18(S3): 301-306.
The interaction terms of the isospin-dependent symmetric energy and Coulomb energy are considered in the quantum molecular dynamics model. The effects of the symmetric energy on the mass distribution and cluster formation in the head on collisions of the systems 20Ne + 20Ne and 28Ne + 20Ne at the incident energy of 30 MeV/u are discussed and the favorable condition for synthesizing neutron-rich isotopes is predicted.
Recent Progress of the Beijing FEL-Realizing Saturated Oscillation
Xie Jialin, Zhuang Jiejia, Huang Yongzhang, Zhang Lingyi, Lin Shaobo, Zhao Changnong, Li Lihua, Wu Gang, Wang Gang, Li Chengze, Su Jing, Zhong Yuanyuan, Wang Yanshan, Li Yonggui, Ying Runjie, Yang Xueping, Li Youmeng, Han Bin, Wu Qingwu, Zhang Yuzhen, Pan Weimin, Wang Jianwei, Zhang Liwen, Guo Kangzhu, Chang Xiangyun, Li Yanan, Dai Lisheng, Xu Jingqiang, Lu Huihua, Wang Bozhi, Reng Liangzhong, Tian Ruisheng, Fu Ensheng
1994, 18(S3): 307-314.
Beijing FEL facility has been built in IHEP, the saturated oscillation was obtained at a wavelength of 10.68 μm, on 28 Dec. 1993. The average output energy and the pulse width were measured to be 3 mJ, 2 μS, respectively. The corresponding oscillation power is greater than 220 kW, peak power is about 20MW, which is about 108 times higher than that of spontaneous emission. The FWHM of the FEL spectral bandwidth is less than 2%. The small signal gain is 32% per pass. The extraction efficiency is 0.48%. In the present experimental results,BEFL can be saturated by changing electron energy at the wavelength range of 9-11 μm,the maximum average output energy and extraction efficiency are 10 mJ, 0.52% respectively, the minimum spectral bandwidth of 0.5% has been achieved by shortening cavity length.
Measurement of Characteristic Positron Annihilation Lifetime in HgCdTe
He Yuanjin, Xin Mingrui, Zhang Tianbao
1994, 18(S3): 315-319.
A new measurement method of characteristic lifetime of positron annihilation in mercury cadmium telluride (MCT) in thermoequilibrium with mercury vapor was proposed. A result of τb the annihilation lifetime of positrons in bulk state in HgCdTe, being 277±lps,and τb, the lifetime of positrons trapped in mercury vacancies,being 306±2ps was obtained. The result was discussed and compared with that from other methods.