1995 Vol. 19, No. 12

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Lifetime Measurement of the 16+ Yrast State in 128Ce
Li Guangsheng, Dai Zhengyu, Wen Shuxian, Li Shenggang, Weng Peikun, Zhang Lankuan, Yuan Guanjun, Yang Chunxiang
1995, 19(12): 1057-1061.
The high spin states in 128Ce were populated with the reaction l00Ru (32S,2p2n)128Ce at an incident energy of 141MeV. The lifetime of the 16+ state was measured by using the Doppler shift attenuation method. The corresponding B(E2) value is compatible with the rotational value of theoretical calculation.
Trigger Efficiency Measurement of BES
Yu Zhongqiang, Zhao Dixin, Gu Jianhui, Guo Yanan, Zhang Bingyun, Ding Huiliang, Li Weidong
1995, 19(12): 1062-1067.
An experimental method to measure the efficiency of the trigger for the BES is introduced. The design of trigger table, event selection and calculation of efficiency are described. The efficiencies of various trigger conditions and event types are given.
Experimental Results of the Off-Line System of He-Jet Laser Ion Source
Xu Sida, Shang Rencheng, Zhang Shuming, Ye Zipiao, Zhang Wei, Zhao Zhizheng, Luo Yixiao
1995, 19(12): 1068-1071.
The off-line system of He-jet laser ion source at Tsinghua University was tested and described briefly. Experimental results of direct resonant ionization of Na atoms at the outlet of He-jet of the system by laser were reported. The results show that in-beam ionization of Na atoms at the outlet of the He-jet is practicable. A laser ion source based on such design will possess good Z selectivity, high efficiency, short delay time, and applicability to refractory elements.
Relative Likelihood and e/π Separation at BES
Ye Shuwei, Chen Hongfang, Wu Jian, Zhang Ziping, Niu Hongquan, Xu Tong, Tong Guoliang, LV Feng, Li Yong, Zeng Jiyang, Wu Yigen, Yi Kai, Chen Xiangyang, Xu Mi
1995, 19(12): 1072-1077.
On the basis of particle identification methods at BES, this paper proposes a so-called relative likelihood method. The method makes the most use of the information provided by the BES, and apparently improves the particle identification efficiency with lower misidentification compared with the simple cut method. With this method, several studies in τ physics were done and good results have been obtained.
Frequency Distributions of Energy Deposition in Low Energy Electron Track
Li Qiang, Wei Zengquan, Ma Shouwu
1995, 19(12): 1078-1083.
Based on our Monte Carlo calculation model, frequency distributions of energy deposition in areas of DNA segment and chromatin fibre segment by a low energy electron are calculated in liquid water. The results are compared with those of OREC code and CPA code. These calculated results are theoretical evidence of soft X ray mechanism which was suggested by us in order to explain physical mechanism of deep biological effect produced by low energy heavy ion implantation.
2-Dimensional Cyclic Representations of Uq(sl(2)), C-GCoefficients and a Free Fermion 8-Vertex Model
Zhang Jun, Yang Guangcan, Yan Hong
1995, 19(12): 1084-1089.
We give explicitly the 2-dimensional cyclic representations of quantum algebra Uq(sl(2)) with central extension. The C-G rule and the C-G coefficients are calculated and the intertwiner for tensor representations in different orders is constructed with C-G coefficients. This intertwiner is shown to be the R-matrix for an eight vertex model that satisfies the free Fermion condition and therefore gives an integrable model.
Analytical Calculation of Lattice SU(2)-Higgs Model with Varied Length
Liu Beishu, Zheng Xite
1995, 19(12): 1090-1095.
The order parameter Ep= of the lattice SU(2)-Higgs model in four dimensions is calculated using the cumulant expansion to the fourth order approximation.The Higgs field is in the fundamental representation. An approach for determining two variational parameters is developed. The phase diagram obtained is in a good agreement with the Monte Carlo result.
Possibility of Detecting Neutral TC Vector Meson
Yue Chongxing, Lu Gongru, Wan Lingde
1995, 19(12): 1096-1099.
We construct the lowest order vector meson operators. Using these operators, we estimate the decay widths of the neutral vector meson ρ in a realistic one family TC (Technicolor) model and discuss the possibility of detecting this particle at pp colliders or at LEPⅡ.
Color Singlet Set of Multiparton System qq+ng
Wang Qun, Xie Qubing
1995, 19(12): 1100-1107.
Color singlet set and color string configuration among partons for multiparton system are analyzed from exact SUc(3). The probability for singlet string, which corresponds to color dipole in Lund CD model, is found to decrease rapidly as the number of gluons increases, while for those singlet clusters whose color structure are similar to glueballs, their probability grows rather fast and is independent of strong coupling constant. This phenomenon is thought to be a kind of collective effect.
Finite Temperature QCD Sum Rule and the ρ-Meson
Liu Jueping, Jin Yaping
1995, 19(12): 1108-1113.
The contributions from the three-gluon condensates to the finite temperature QCD sum rule for the ρ-meson are calculated, and then the dependence of the properties of the ρ-meson upon temperature is investigated in a string model of condensates. Our results show that the parameters characterizing the properties of the ρ-meson change noticeably When the temperature closes to the critical temperature of the condensates, and if the critical temperatures of condensates are the same.
Pre-equilibrium GDR Built on Dinucleus
Zhong Jiquan, Wen Wanxin, Jin Genming, Di Tori
1995, 19(12): 1114-1118.
The properties of GDR built on the long-lived dinucleus formed in the process of fusion reaction above Coulomb barrier induced by mass symmetric and mass asymmetric entrance channels are discussed. The calculated result shows that the GDR energy of dinucleus split into two peaks in the energy spectrum.