1995 Vol. 19, No. S4

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Energy Spectrum of Primary Cosmic Rays at the “Knee” Region Observed with the Huairou Air Shower Array
Luo Guangxuan, Tan Youheng, Zhang Chunsheng, Dong Yuju, Yuan Peng, Zhang Huimin, Wang Hui, Yuang Yukui, Li Jing
1995, 19(S4): 325-331.
Careful analysis has been made of 650,000 EAS events recorded by the Huairou EAS Array. The size spectrum and energy spectrum of primary cosmic rays in the range of 1015 to 5×1016 eV are obtained. The energy spectrum shows a clear and smooth "knee" structure around 3×1015eV. Except for the smooth bending feature of the "knee," it is consistent with the Akeno spectrum. Under the assumption of the so-called rigidity dependent cut model, by adjusting the bending energy Ec of the primary proton spectrum in the Monte Carlo simulation and comparing with the experimental spectrum, we found that the proper value of Ec is in the energy range of 160 to 240T eV.
High-Performance Detector System of TR4 Sit at HIRFL
Guo Zhongyan, Zhan Wenlong, Xi Hongfei, Zhou Jianqun, Zhao Youxiong, Feng Enpu, Wang Jinchuan, Luo Yongfeng, Lei Huaihong
1995, 19(S4): 333-340.
The update structure and specification of the high-performance detector system is described in this article. It consists of Si multiunit telescopes, IC-f PSD+SPD+CsI(Tl) logarithmic density telescopes, projectilelike fragment TOF telescopes, 3×3 and 6×6 CsI(Tl) scintillator arrays, and Si+CsI(Tl) light particle telescopes. The ZZ~50, ΔE/E~0.3% for Si telescopes; ZZ~44.5, Δx~1.7 mm for logarithmic density telescope; and AA~86, Z/AZ-48, ZZ~0.78%, ΔE/E~286 ps for projectilelike fragment TOF telescope focusing with ellipsoidal surface mirror are obtained.
Study of Level Structure in Neutron-Deficient 197Bi
Zhou Xiaohong, Sun Xiangfu, Guo Yinxiang, Lei Xiangguo, Liu Zhong, Chen Xinfeng, Zhang Yuhu, Jin Hanjuan, Luo Yixiao, Wen Shuxian, Yuan Guanjun, Li Guangsheng, Yang Chunxiang
1995, 19(S4): 341-347.
High-spin states of 197Bi are populated by bombarding a thick natural Re target with 16O beams of 100 MeV. Using comprehensive γ-γ-t coincidence measurements, three new isomers of 197Bi are confirmed, 11 new γ-transitions are identified, and errors in the existing level scheme are corrected. According to the systematic level structure of odd-A Bi isotopes, the configuration and decay property of the new isomer of 197Bi with t1/2=19.3±4.9 ns are discussed. The γ-ray angular distributions are also measured. A new level scheme of 197Bi is proposed.
Fractal Analysis of Pseudorapidity Distribution Fluctuation in 400 GeV/c pp Collisions
Wang Shaoshun, Zhang Jie, Xiao Chenguo, Ye Yunxiu, Zhong Yu, Shen Tianguang
1995, 19(S4): 349-355.
The fractal behavior 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.
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(S4): 357-361.
The high-spin states in 128Ce were populated with the reaction 100Ru(32S,2p2n)128Ce at an incident energy of 141 MeV. 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.
Experimental Results of the Off-Line Test Setup of Laser Ion Source
Xu Sida, Shang Rencheng, Zhang Shuming, Ye Zipiao, Zhang Wei, Zhao Zizheng, Luo Yixiao
1995, 19(S4): 363-367.
The off-line test setup of the laser ion source built in Tsinghua University is described briefly. The experimental result of laser resonant ionizing Na atoms carried by He gas at the outlet of He-jet are presented. The results indicate that the in-beam ionization of Na atom is viable. Based on these results, vve can design a laser ion source that has high Z selectivity,-high efficiency, low limits of lifetime for isotopes being studied, and is applicable for studying refractory elements.
Frequency Distributions of Energy Deposition in a Low-Energy Electron Track
Li Qiang, Wei Zengquan, Ma Shouwu
1995, 19(S4): 369-373.
Based on our Monte Carlo calculation model, the frequency distributions of energy deposition in areas of DNA segment and chromatin fiber segment by low-energy electrons are calculated in liquid water. The results are compared with those of OREC code and CPA code. These calculation results provide the theoretical evidence of a soft X ray mechanism, which was suggested by us to explain the physical mechanism of deep biological effects by ultra-low-energy heavy ion implantation.
Proof of “Irreducible Postulation” and Its Applications
Zou Pengcheng, Huang Yongchang
1995, 19(S4): 375-378.
The "irreducible postulation" in group theory is first proved and applied to the classification of quantum states. This postulation assumes that, after considering the whole symmetry of a system, the degeneracy space of any energy level must be an irreducible space of its symmetric group. It also means that the accidental degeneracy does not exist, in fact, if the whole symmetry of a system is found.
A Calculation for Transport Coefficients of Quarks in QGP Under the Relaxation Time Approximation
Bai Ge
1995, 19(S4): 379-387.
Using the kinetic equation and considering the effect of the mean field, the transport coefficients of quarks in QGP under the relaxation-time approximation are calculated, and the viscous effect and thermal conductive effect of QGP are discussed.
In-Medium Nucleon-Nucleon Cross Sections in the Nonrelativistic Energy Region
Ge Lingxiao, Zeng Xianghua
1995, 19(S4): 389-396.
In this paper, the nucleon-nucleon collision cross sections σnn in medium in the nonrelativistic energy region are calculated using the Skyrme interaction. The energy and density dependence of nucleon-nucleon collision cross sections in medium and the influences of different Skyrme parameters on the in-medium cross section are discussed. It is found that the in-medium nucleon-nucleon collision cross sections are larger than the free nucleon-nucleon collision cross sections with Pauli corrections at lower densities, and σnn in medium above a special energy is larger than the free one at higher densities.
Finite-Temperature Thermodynamic Potential of Two-loop QED and the Overlapping Divergences in Arbitrary Gauge
Hou Defu, Li Jiarong
1995, 19(S4): 397-404.
Dimensional regularization at finite temperature is applied to calculate accurately the thermodynamic potential of two-loop QED and the overlapping divergences in arbitrary gauge. The calculation indicates that the overlapping divergences cancel each other and the result is gauge-independent.
Construction of Paired States in Axially Symmetric Nuclei
Zeng Jinyan, Lei Yian, Wu Wenqing
1995, 19(S4): 405-411.
The construction of paired states of a quantum many-particle system is intimately connected with its symmetry. In the cranked shell model of axially symmetric nuclei, three possible forms of paired states can be constructed (i.e., monopole pair, ±Ω pair, and signature pair), which are the simultaneous eigenstates of (J2, J3, J3)and(J32, R1(π)), respectively. When only the pairing interaction is considered (ω=0), the energy spectra obtained are the same for the three types of pairing interactions. When the system is cranked (ω≠0), owing to different behavior of the paired states under rotation, the co variation of the spectra and related properties of the system may be different to some extent.
Microscopic Studies on the Ground State Properties of the Nucleus 100Sn
Ren Zhongzhou, Xu Gongou
1995, 19(S4): 413-420.
The binding energy and the root-mean-square radii of the matter, proton, and neutron distributions for the doubly magic nucleus 100Sn have been calculated using the relativistic and nonrelativistic mean-held theories. The results from the two mean-held theories are compared and discussed. This is the first microscopic calculation for 100Sn.
Dilepton Invariant Mass Distribution in Central Rapidity Region
He Zejun, Zhang Jiaju
1995, 19(S4): 421-425.
The Boltzmann approximation of the phase-space distribution function of quarks and pions, adopted by previous authors, is generalized to a complete expression. After calculating the density of particles based on the temperature of the central rapidity region, we study the dilepton production in Bjorken's (1+1) dimensional scaling expansion system and find that the generalized approximate distribution function significantly changes the characteristic dilepton distribution predicted when assuming quark matter formation.