1998 Vol. 22, No. 05

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Review
β-Delayed Proton Emission Precursor 87Mo
Huang Wenxue, Ma Ruichang, Xu Shuwei, Xu Xiaoji, Xie Yuanxiang, Li Zhankui, Ge Yuanxiu, Wang Yanyu, Wang Chunfang, Zhang Tianmei, Sun Xiangfu, Jin Genming, Luo Yixiao
1998, 22(05): 385-387.
Abstract:
The decay of the nuclide 87Mo has been studied with p-γ coincidence measurement. The proton branches in the decay of 87Mo populating the first (2+), (4+) and (6+) excited states of 86 Zr were measured to be (11±6)%, (2±l)% and (2±l) %, respectively, which revised the previous results.
Electron Identification in the Measurement of MichelParameter in τ Lepton Decay
Qian Chengde, Feng Sheng, Tong Guoliang, Wu Yigen
1998, 22(05): 388-392.
Abstract:
The Michel parameter ρτ→e is determined through studying the electron energy spectrum of τ→eνν decay by Beijing Spectrometer(BES). This paper describes the electron identification with dE/ dx、β、E/p informations for charged particles and their, adequate combinations using e+e collision data collected at s=4.03GeV.
Study of Isotopic Distributions of the Fragments from the 25MeV/u 40Ar Induced Reactions
Lin Yuangen, Zhan Wenlong, Guo Zhongyan, Zhou Jianqun, Zhao Youxiong, Liu Guanhua, Wang Jinchuan, Luo Yongfeng, Lei Huaihong, Qi Zhong, Zhang Wansheng, Qin Lijun
1998, 22(05): 393-397.
Abstract:
The forward emitted fragments in 25MeV/u 40Ar induced reactions with 27Al,58Ni,115In targets are measured. The isotopic distributions are investigated, and the relation of the targets with the fragments' N/Z is given. Finally the source emitting fragments is briefly analysed.
Study of the Unusual Performances of One Type DriftChamber Feedthrough
Wang Yunyong, Wang Shaomin, Mao Huishun, Liu Rongguang, Li Rubai, Li Jin, Song Xiaofei, Zhang Jian, Zhang Dehong, Jin Yan, Huang Jundong, Ke Zunjian, Gao Shuqi, Xie Peipei, Yan Jie, Gu Jianhui, Li De
1998, 22(05): 398-405.
Abstract:
The unusual performances of one type of drift chamber feedthrough have been studied. It is an aging effect. The relationship of dark current and random noise with time, high voltage and temperature has been tested.
One Generation Technicolor Model and Single TopProduction Process qq→tb
Lu Gongru, Huang Jinshu, Cao Yigang, Yue Chongxing
1998, 22(05): 406-412.
Abstract:
One-loop corrections from the Pseudo-Goldstone bosons (PGBs) in the one generation technicolor model (OGTM) to the single top-quark production via qq→tb at the Fermilab Tevatron are calculated. We find that the maximum corrections to the total cross section for the single top-quark production at the Fermilab Tevatron may reach -15.3% relative to the tree-level cross section, which can be tested at a high-luminosity Tevatron.
A Study on Infinite Number of Integrals of Motion ClassicallyIntegrable System With Boundary (Ⅰ)
Chen Yixin, Luo Xudong
1998, 22(05): 413-423.
Abstract:
By the zero curvature condition in classically integrable system, the generating funtions for integrals of motion and equations for solving K± matices are obtained in two-dimensional integrable systems on a finite intervel with independent boundary conditions on each end. Classically integrable boundary conditions will be found by solving K± matrices. In this paper, we develop a Hamiltonian method in classically integrable system with independent boundary conditions on eath end. Our result can be applied to more integrable systems than those associated with E.K. Sklyanin's approach.
Pion Source Density Distribution and Tow-Pion Interferometry atSmall Relative Momentum in Relativistic Heavy-Ion Collisions
Chen Xiaofan
1998, 22(05): 424-428.
Abstract:
The relations among the space-parameters, average radii and root-mean-square radii of the different pion source density distributions are obtained with the power series expansion of the two-pion correlation functions at the small relative momentum. The results are in good agreement with the experimental measurement of the central collisions 1.8A GeV Ar+Pb. The average radius and root-mean-square radius of the above reaction are given. The values of k=2>/2 for the different source density distributions are calculated.
Simulation of Heavy-Ion Collision With Isospi-Separated RVUU Model
Chu Zili, Zheng Yuming
1998, 22(05): 429-433.
Abstract:
We generalize the previous RVUU model to he able to identify the isospin degree of freedom of particles. This modified model is used to simulate the particle production in Au+Au collision at 1GeV/u. The calculated momentum spectra of p, π+ and K+ particles and multiplicities of the π+ and K+ and the ratio K++ as a function of the number of participatiang nucleons agree very well with experimental data. The physical origin of the ratio K++ as function of participating nucleons is discussed.
Reduction of Strange Quark Suppression in Relativistic Nucleus-Nucleus Collisions
Tai An, Sa Benhao
1998, 22(05): 434-439.
Abstract:
We use the event generator LUCIAE with the mechanism of reduction of strange quark suppression to investigate the strangeness enhancement in relativistic nucleusnucleus collisions. The results of LUCIAE reproduce the corresponding NA35 data quite well and explain very well that the reduction of strange quark suppression plays more important role than the rescattering of final state hadrons in the production of strange particles.
Renormalization of g-Boson Effects Under Weak Coupling Condition
Zhang Zhanjun, Sang Jianping, Yang Jie, Liu Yong
1998, 22(05): 440-445.
Abstract:
An approach based on purturbation theory is proposed to renormalize g-boson effects for sdglBM system, which modifies that presented earlier by Druce et al. The weak coupling condition as the usage premise of the two approaches is proved to be satisfied. Two renomalization spectra are calculated for comparison and analyses. Results show that the g-boson effects are renormalized more completely by the approah proposed in this paper.
Comparison Between the Harris and ab Expressions for the Descriptionof Nuclear Superdeformed Rotation Bands
Hu Zuoxian, Zeng Jinyan
1998, 22(05): 446-451.
Abstract:
The superdeformed rotational bands in the A≈190 region are systematically analyzed using the Harris two-parameter formula and the ab expression, respeclively. Similar to the situations in normally deformed nuclei, there exist obvious and systematic deviation of Harris formula from the experiments, In contrast, the prediction of ab formula is very close to experiments, and can be conveniently used for the description of nuclear superdeformed bands.
η Photoproduction off the Deuteron
YU Tao, Jiang Huanqing
1998, 22(05): 452-459.
Abstract:
The η meson photoproduction off deutron γ d→ηX are calculated, where assuming the η photoproduction from nucleon is dominated by the N11*(1535), and the η-nucleon-nucleon vertex matrix element Γdpn is approximated using the non-relativistic deuteron wave function. The cross section and differential cross section can fit the new data well, and the coupling constant of γnN* is obtained.
Dimensional Regularization and Analytical Continuationat Finite Temperature
Chen Xiangjun, Liu Lianshou
1998, 22(05): 460-465.
Abstract:
The relationship between dimensional regularization and analytical conti- nuation of infrared divergent integrals at finite temperature is discussed and a method of regularization of infrared divergent integrals and infrared divergent sums is gevin.
Hadronic Masses in Hot Matter in an Effective Chiral Lagrangian Approach
Chen Hong, Liu Bo
1998, 22(05): 466-474.
Abstract:
The thermal masses of hadrons are calculated in the effective chiral Lagrangian which reproduces the scaling anomaly of QCD. It is found that the thermal masses of constituent quark and scalar field decrease faster in one-loop approximation than in mean-field aproximation, whereas the pion at the chiral limit remains massless at all temperatures.
Upgrade of BPM System for the BEPC Storage Ring
Ma Li, Shi Ping, Ye Kairong
1998, 22(05): 475-480.
Abstract:
The beam position monitoring (BPM) system for the storage ring of the reproducibility of the measurement is better than 10 microns. The measurement timefor scanning all BPMs is about 11 seconds.The dynamic rang of the system is over81 dB and the minimum measurable beam intensity is less than 0.5mA.The reliabilityof the measurement s assured by the self-consistency check.