1995 Vol. 19, No. 11

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Study of Excited States in Neutron-Deficient 197Bi
Zhou Xiaohong, Sun Xiangfu, Guo Yingxiang, Lei Xiangguo, Liu Zhong, Chen Xinfeng, Zhang Yuhu, Jin Hanjuan, Luo Yixiao, Wen Shuxian, Yuan Guanjun, Li Guangsheng, Yang Chunxiang
1995, 19(11): 961-967.
High-spin states in 197Bi were populated by bombarding natural Re target and isotope 187Re target with 16O beam of 100 MeV. Using comprehensive γ-γ-t coincidence measurements,three new isomers in 197Bi were established and eleven new y-transitions were identified,while errors in the existing level scheme were corrected.From the level structure systematics of the odd-mass Bi isotopes, the configuration and decay properties of a new isomer with t1/2n=19.3±4.9ns in 197Bi were discussed.The y-ray angular distributions were also measured.A new level scheme of 197Bi was proposed.
Fractal Analysis of Pseudorapidity Distribution Fluctuation in 400GeV/c pp Collisions
Wang Shaoshun, Zhang Jie, Xiao Chenguo, Ye Yunxiu, Zhong Yu, Shen Tianguang
1995, 19(11): 968-973.
The fractal behaviour of multiplicity production in 400 GeV/c pp collisions is analyzed using the modified multifractal moments.The generalized dimensions Dq,q=2—5,are calculated.A comparison with the results obtained by the method of scaled factorial moments has been made. The results show that the multifractal character is observed.The fractal analysis method proposed by Fujio Takagi has been tested.
Intensities of Inverse Compton Gamma-Rays in Galactic Medium Latitude
Zhang Li
1995, 19(11): 974-979.
The gamma-ray emissivity q/4π of galactic cosmic rays interacting with inter-staller gases at medium-latitude(|b|=10°—20°)is determined by using recent EGRET data. Meanwhile the method to obtain the emissivity by gamma-ray data themselve is adopted,and then the inverse compton (IC ) integral intensities as a function of galactic longitude are obtained. The differential IC intensities averaged over all galactic longitudes can be expressed by IIc(E)=1.58×10-6E-2.08±0.06cm-2·s-1·sr-1GeV-1,b=10°—20°and IIc(E)=2.08×10-6E-2.03±0.06cm-2·s-1·sr-1GeV-1,b=-20°—-10° for b=-20°—-10°,where the energy range is from 30 MeV to 4 GeV.
Study of Production of Secondary Beams from 95MeV/u 12C Projectile
Yang Yongfeng, Roussel Chomaz
1995, 19(11): 980-986.
A systematic study about the production of secondary beams in 95MeV/u 12C+Be,Cu and An targets was performed by using the GANIL doubly achromatic spectrometer LISE.The maximum values of the secondary beam production calculated by programs LISE and INTENSITY are in agreement with the experimental results for the secondary beams near the β stability line.However,the calculations are larger than the experimental results for the secondary beams far from the β stability line.The optimum target thickness for the production of secondary beams corresponds to about 30% beam energy loss in the target.Beryllium target was found to offer higher production for all the secondary beams than copper and gold targets.
Improved Measurement of γ-Energy from Parapositronium 2γ-Decay
Peng Liangqiang, Zhang Tianbao, Wang Haidong, Meng Bonian, Yin Guoli
1995, 19(11): 987-990.
Using a silica aerogel sample with oxygen gas filled as the positronium(Ps)source and a time selecting energy spectrometer,the measurement of the y-energy of parapositronium(p-Ps)2y-decay is further improved and the result of hv=510995. 34±0.69eV is obtained by a slithering comparison with the precisely known y-energies of 192Ir.The rest mass of a pair of positron and electron is determined by the correction with the binding energy of Ps,which shows a mass equality within 1.4ppm between positron and electron by the comparison with the rest mass of electron.
Target Residues from the Interaction of Copper with 40MeV/u 40Ar Ions
Yin Xinmin, Li Wenxin, Zhang Xiang, Sun Tongyu, Shizuko Ambe, Yoshitaka Ohkubo, Masako Iwamoto, Yoshio Kobayashi, Fumitoshi Ambe
1995, 19(11): 991-997.
Cross Sections and average forward recoil range FW were measured for target residues from the interaction of Cu with 40MeV/u 40Ar ions using off-line y-ray spectroscopy.The mass yield distribution was obtained with assumption of charge distribution.The linear momentum transfer was calculated from FW values.A comparison with similar results of 12C+Cu and 20Ne+Cu reactions indicates that the fractional linear momentum transfer,corresponding to central collisions,decreases with increasing projectile mass at the same energy per nucleon. However,the excitation energy of the composite system created from the collisions of Cu with 40Ar ions reached the value of 5.3MeV /u and was higher than those from the collisions with 12C and 20Ne ions.
Finite-Temperature Thermodynamic Potential of Two-Loop QED and Overlapping Divergences at Arbitrary Gauge
Hou Defu, Li Jiarong
1995, 19(11): 998-1004.
The dimensional regularization at finite temperature is applied to calculate accurately the thermodynamic potential of two-loop QED and the overlapping divergences at arbitrary gauge.It indicates that the overlapping divergences are cancelled with each other and the result is gauge-independent.
Two Dimensional Cyclic Representations of Uq(sl2)and 8-Vertex Ising Model
Zhang Jun, Yang Guangcan, Yan Hong
1995, 19(11): 1005-1011.
We give explicitly the 2-dimensional cyclic representations of quantum algebra Uq(sl2)with central extension.The intertwiner for tensor representations in different ordersis constructed with C-G coefficients.This intertwiner is shown to be the R -matrix for eight vertex Ising model.
Canonical Quantal Symmetry in a Dynamical System
Li Ziping
1995, 19(11): 1012-1018.
Starting from phase-space generating functional for the system with regular and singular Lagrangian respectively,the canonical Ward identities under the global symmetry transformation in phase space are deduced.The corresponding local transiormation is studied,the conserved charge is obtained at quantum level and the canonical Noether theorem in quantum case is given.The preliminary application of the results to a system of interacting nucleons and pious is discussed.
Strange Baryon and the Signal of QGP Formation in Ultrarelativistic Nucleus-Nucleus Collisions
Sa Benhao, Tai An, Lu Zhongdao
1995, 19(11): 1019-1023.
The ratios of strange baryon to antibaryon produced in the reaction S+ Pb at 200 AGeV beam energy are computed using new version of Fritiof with collective string interaction and rescattering.Theoretical ratios of and are comparable with experimental data within the range of the deviation among the data of different collaborations.It seems to indicate that these data of the ratios of strange baryon to antibaryon might be explained in the hadronic scenario.
Bandcrossing of K=1/2 Bands in Odd - Proton Nuclei
Wu Chongshi
1995, 19(11): 1024-1028.
The bandcrossing in the K=1/2 bands of odd-A nuclei was discussed in the particle-rotor model.The decoupling term in the rotational energy expression has a remarkable effect on the backbending frequency,which,in the band built on the [541]↓orbital,leads to a bandcrossing delay comparable with the observa tions.
Microscopic Studies on Ground State Properties of the Nucleus 100Sn
Ren Zhongzhou, Xu Gongou
1995, 19(11): 1029-1035.
The average binding energy,the radius of proton distributions and the radius of neutron distributions for the nucleus 100Sn have been calculated by the relativistic mean-field theory and the nonrelativistic mean-field theory.The numerical results by two methods have been compared and discussed.This is the first microscopic calculation on 100Sn.
Dilepton Invariant Mass Distribution in Central Rapidity Region
He Zejun, Zhang Jiaju, Qiu Xijun
1995, 19(11): 1036-1039.
The Boltzmann approximation of the phase-space distribution functions of quarks and of pious, previously adopted by the authors,is generalized to a complete expression.After calculating the density of particles from the temperature of the central rapidity region,the dilepton production in Bjorken's(1+1)dimensional scaling expansion system is studied.We find that the generalized approximation distribution function significantly changes the characteristic dilepton distribution for the prediction of the quark matter formation.
Multifragmentation Process in HIC Simulated by Modified Quantum Molecular Dynamics
Liu Hang, Liu Jianye, Zhang Shaoguang, Li Junqing
1995, 19(11): 1040-1046.
The collision dynamics and yields of the multifragmentation in intermediate energy heavy ion collisions are simulated within the frame of the modified quantum molecular dynamics(MQMD ).With this new MQMD,it is found that the obvious improvements about the agreements between the experimental data and the simulating results for the fragment production by means of MDI and Pauli potential are achieved.Meanwhile the different influences of MDI and Pauli potential on the collision dynamics of intermediate energy heavy ion collisions are obtained.Finally the possible reasons for the discrepancies between the experimental data and the present simulating results and remedies of these deficiencies are discussed in detail.
Microscopic Mechanism of Stretching Effect of γ-Soft Nuclei
Wu Lianao, Ding Huiming
1995, 19(11): 1047-1051.
Using the Fermion Dynamical Symmetry Model (FDSM ),we give the microscopic mechanism of the stretching effect of the y-soft nuclei. The results of numerical calculation show that the relative errors between the calculated results and data are not beyond two percent.
Effect of Beam Measurement Error on Damping System
Xu Jianming
1995, 19(11): 1052-1056.
The effect of the beam measurement error on the damping system has been studied.This error will reduce the damping speed and induce a closed orbit distortion.