1998 Vol. 22, No. 11

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Measurement of Michel Parameter in τ Decay
BES Collaborator
1998, 22(11): 961-968.
We have analysed the e+e collision data collected with Beijing Spectrometer at the center-of-mass energy 4.03 GeV and selected e+e→τ±τ+→e±X+v's events, X± required as μ±、π± and ρ±. From fitting electron energy spectrum in τ→ev's decay, the measurement value of Michel parameter is given as ρτ→e=0.705, this result is in good agreement with the prediction of standrd Model.
Independent Yield Measurement for the Hg-Isotope Products From 600 MeV 18O+natPb(thick target) System (Ⅰ) Experiment and Technique
Zhang Li, Zhao Jinhua, Zheng Jiwen, Qin Zhi, Yang Yongfeng, Zhang Chu, Wang Jicheng, Guo Tianrui, Jin Genming, Hu Qingyuan
1998, 22(11): 969-976.
With an on-line, gas-thermochromatographic Hg element separation as well as a special detection technique, the independent cross sections of the radioactive Hg-isotopes produced from a 600MeV 18O +natPb(thick target) reaction system were determined. The independent cross sections of 22 Hg-isotope nuclides in the mass range from 180Hg to 209Hg were measured. The experimental set-up, the detection technique, the γ-spectrum analyses and the extraction method of production cross sections based on the γ activities from the successively decaying daughter nuclei were described.
Rem-Meter Correction Factor for High Energy Neutron Outside Concrete shielding
Li Guisheng
1998, 22(11): 977-981.
For the 10 inch diam. single-sphere rem-meter and the standard A-B rem-meter placed outside the concrete shielding wall, correction factors for measuring the high energy neutron dose equivalent produced by intermediate energy heavy ion reaction have been calculated taking into account the energe response of the rem-meter and the effect that the neutron spectra become remarkably "harder" after penetrating through a concrete shielding wall.
Track Reconstruction in Vertex Chamber of BES-Ⅱ
Chen Guangpei, Yuan Ye, Mao Zepu, Bai Jinzhi, Sun Hansheng, Liu Jing, Li Weiguo, Zhang Changchun, Yan Wuguang, Li Peiqin, Qiu Jinfa, Yang Jie, Yang Chunmin, Rong Gang, Zhen Jianping, Zhao Haiwen, Zhao Meng, Xie Yu
1998, 22(11): 982-989.
This paper describes the algorithm of the non-numerical pattern recognition used in the VC of BES-Ⅱ. The code is good to provide the spacial resolution and the effeciency of the track found by M.C. data and experimental data.
Measurement of the τ Polarization Asymmetry in τ→a1 v→π±π0π0v Decay at Z0 Peak
Liu Zhenan, Chen Guoming, Chen Hesheng, Tang Xiaowei
1998, 22(11): 990-995.
The τ polarization asymmetry in τ→a1v→π±π0 π0v decay at Z0 peak is measured using data collected by L3 detector at LEP in 1992 and 1993, Apol=-0.239±0.126±0.100, where the first error is statistical and the second systematic. And the effective electroweak mixing angle sin2θw=0.2197±0.0219 is derived.
SU(3)C×SU(2)I×U(1)Y Theory of Composite Leptons
Liu Yaoyang, Sun Lazhen, Jiang Xiangdong
1998, 22(11): 996-1003.
Assuming Higgs Assuming coupling to be the only origin of parity non-conservation, an SU(3)C×SU(2)I×U(1)Y theory of composite leptons is established in the Scheme of three generations and supersymmetry.
Nonlinear Response Equation of Non-Abelian Medium to EXternal Source
Zheng Xiaoping, Li Jiarong
1998, 22(11): 1004-1012.
The kinetic equations for a quark-gluon plasma (QGP) are effectively expanded in terms of fluctuating field using weak turbulent theory. The nonlinear response equation of QGP is derived.
Three-Dimensonal Langevin Approach to Kinetic Energy and Mass Distribution of Fission-Fragments
Bao Jingdong
1998, 22(11): 1013-1019.
A three-dimensional Langevin equation with covariant form is applied to describe the asymmetric nuclear fission. The calculations for kinetic energy and mass distribution of fission-fragments are performed in terms of the {c,h, α} parameterization,and the descent process of the fissioning nucleus from the saddle point to the scission point is simulated numerically. The dependence of the model on the choices for two types of nuclear dissipation such as two-body viscosity and one-body dissipation, as well as the scission configurations of nuclear system with finite neck is investigated.
Angular Momentum Projected Deformed HF Spectra of 46Ti and 48Cr With MSDI
Han Yong
1998, 22(11): 1020-1028.
Taking the modified surface delta interaction (MSDI) and using a spherical shell model basis set, we carry out the deformed Hartree-Fock (HF) calculation for the even-even nuclei 46Ti and 48Cr in the fp shell, and construct the deformed HF intrinsic states which are the Slater determinants from the HF single-particle states.The angular momentum projection program is then carried out and the reasonable results are obtained.
Influence of Configuration Admixtures on Superdeformed Triaxial Bands
Xing Zheng, Wang Zixing, Chen Xingqu, Xu Jinzhang
1998, 22(11): 1029-1034.
A detailed analysis of superdeformed triaxial bands is made with the particle-rotor model. The influence of configuration admixtures between different j subshells on such systems is investigated. In order to identify the superdeformed triaxial bands both the energy spectra and electromagnetic transition probabilities should be fitted with the experimental data simultaneously.
Isospin Effects on Collective Flow in HIC at Intermediate Energies
Chen Liewen, Zhang Fengshou, Zeng Xianghua, Jin Genming
1998, 22(11): 1035-1041.
Based on an isospin-dependent quantum molecular dynanics model, the neutron and proton density calculated from Skyrme-Hartree-Fock theory, along with the neutron and proton Fermi momenta calculated from Fermi gas model, are used to sample stable initial nuclei, 58Fe and 58Ni. The isospin effects on collective flow in reaction systems 55MeV/u 58Fe+58Fe and 55MeV/u 58Ni+58Ni are studied in detail.At different impact parameters for different types of fragments, it is shown that the neutron-rich system 58Fe+58Fe has stronger collective flow than the system 58Ni+58Ni,which could qualitatively agree with the results of the experiments. Meanwhile, the effects of both isospin-dependent symmetry energy and nucleon-nucleon cross sections on collective flow are studied.
Preliminary Design of a Dedicated Proton Therapy Linac
Zhou Linong, Zhang Mutian, Luo Zihua, Yu Qingchang, Kong Dengming, Qiao Jimin
1998, 22(11): 1042-1049.
Preliminary design of a dedicated proton therapy linac (S-band) is described.The short beam pulse width and high repetition rate make the linac similar to the electron linacs now used for cancer therapy. This linac consists of ion source, RFQ,DTL, SCDTL, and SCL. Its tatol length is 26m. The final energy of the output proton beam is 70-200MeV, with average beam current of 10-40nA.
Linear Theory of Ion Trapping and Its Application
Zhang Chuang
1998, 22(11): 1050-1056.
The conditions for ion trapping are studied in the case of uniformly distributed electron bunches and bunch trains in storage rings based on the linear theory. The formulas of the threshold current for ion trapping are derived by means of the Twiss parameters in the ion focused system. Based on the theory, the beam behavior observed in the dedicated synchrotron radiation operation of the Beijing Electron-Positron Collider (BEPC) is discussed. It is proposed to apply the bunch than in the BEPC storage ring in order to overcome the beam lifetime drop during the single electron beam operation.