1994 Vol. 18, No. 7

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A Semi-Experimental Method to Determine the Efficiency of Selecting ττ→eμ(v)
Chen Hongfang, LV Feng, Tong Cuoliang, Wu Jian, Wu Yigen, Xu Mianhai, Xu Yadi, Xu Mingkang, Ye Shuwei, Yu Yankua, Zeng Jiyang, Zhong Chongchang, Zhu Hongguo
1994, 18(7): 577-582.
The efficiency of event selection is an important parameter in the measurement of r lepton mass.In our study we use so-called semi-experimental method in which we combine M.C. events and experimental data. With this method the efficiency of selectingττ→eμ(v) is obtained as (14.5±0.7±0.8)%,and various relevant corrections are discussed. The result is consistent with that derived from two-parameter fitting of τlepton mass.
Angular Distribution of Process e+e→τ+τ→a1υτ,a1→ρπ and Characteristics of a1 Meson
Yu Hong, Shen Qixing, Zhang Lin
1994, 18(7): 583-590.
The density matrix and helicity formalism of angular distribution of process e+e→τ+τ→a1υτ,a1→ρπ have been obtained. The helicity amplitude ratios corresponding to the form factors of the W-a1 transition and the strong interaction vertex a1ρπ are determined by the sectionalized fitting method. A model-independent method for determining the mass and width of the wide resonance a1 is given.
The Pseudo-scalar Solution of Bethe-Salpeter Equation in the Approximation of One Gluon Exchange
Bian Jianguo, Wang Jiahui
1994, 18(7): 591-600.
The integral Bethe-Salpeter equation in the approximation of single gluon exchange in momentum position is converted to a differential equation, and all the components of the pseudo-scalar solution of the equation for a vanishing total fourmomentum,including the Goldstein solution as the first component, are derived.
Model Dependence of the BSW Approach
Luo Chuanwang, Huang Tao, Guo Xinheng, Li Jinping, Lu Gongru
1994, 18(7): 601-615.
Hadronic model wavefunctions are applied to calculate hadronic matrix elements of decays of D,B mesons in the Baner-Stech-Wirbel(BSW) approach we have analyzed several different models of valence Pock state wavefunctions, studied their properties and calculated branch ratios of exclusive decays of D, B mesons. The resultsshow that predictions of the different wavefunction models can fit most of the present data within the errors by choosing reasonable a1,a2. Therefore, it will be helpful for studying the model dependence and the reliability of the BSW approach from further theoretical investigation on factorization of weak processes and on the hadronic wavefunctions and from the further precisely experimental measurements.
Dynamics of Many-Body Correlation Green's Functions Ⅳ. Relativistic Generalization
Zuo Wei, Guo Hua, Wang Shunjin
1994, 18(7): 616-620.
By using the generating-functional technique, the dynamics of many body correlation green's functions is generalized to the relativistic case and two sets of equations for the correlation green's functions are derived respectively for the scalar φ3-model and the Yukawa model, which are non-perturbative in nature and provide physically transparent truncations with respect to the order of correlations.
On the Intermittency and Correlation Integral of Multiparticle Final States in High Energy Collisions
Zhang Yang, Hu Yuan, Wu Yuanfang, Liu Lianshou, Zhang Yonghe
1994, 18(7): 621-629.
It is shown by both theoretical analysis and Monte Carlo simulation that using correlation integral instead of factorial moments in the investigation of intermittency phenomena will change the anomalous scaling behaviour in the decreasing of rapidity bin. It is pointed out that the correlation lintegral and. factorial moments probably bin. It is pointed out.that the correlation integral and factorial moments probably reflect different physical aspects. In order to eliminate the artificial factor in bindivision, a method of randomly moving the starting point of bin-division in the investigation of factorial moments is proposed. It is also shown that the spiky events have important contribution to the intermittency indices.
Absorption Correlation in Pion Interferometry Analyses
Huo Lei, Zhang Weining, Wang Shan, Liu Yiming
1994, 18(7): 630-636.
The effect of absorption correlation on the analyzed results of pion interferometry is studied. The way to remove this effect is discussed by using the data from VUU simulation. The data for collisions of 1.8A GeV Ar+Pb at the Bevalac streamer chamber are analyzed. The spatial parameter of the source extracted from pion interferometry is less than the true value due to the absorption correlation. The effect of absorption correlation can be eliminated by properly constructing the background.
The Exact Energy Spectra of States with Good Quasi-Spin in the Double-Quasi-Spin Model
Liao Jizhi
1994, 18(7): 637-646.
Two new forms of the constrained Hartree-Fock(CHF) methods are proposed,and their solutions are discussed in SU(2)×SU(2) Double-quasi-spin model. The diagonalization methods for establishing the exact solutions |JK>and |J> are discussed. It is found that the two kinds of CHF spectra possess the characters of the rotational spectra, and that the new prescriptions are the effective methods to obtain the spectra with multi-band structue.
A Study of Reaction Mechanism in Intermediate Energy Proton-Nucleus Collisions
Lu Zhaoqi, Li Zhuxia
1994, 18(7): 647-651.
The reaction mechanism in p+56Fe collisions with EP=200, 585 and 1000MeV is investigated by Quatum Molecular Dynamics model. The spectra of emitted nucleons, double differential cross sections of emitted neutrons and time evolution of mass distribution of residual fragments are calculated and reasonable results obtained.
Analysis of J/ψ Absorption Cross Section in Relativistic Heavy Ion Collisions
Liu Bo, Zhao Weiqin
1994, 18(7): 652-657.
Based on geometric model the absorption length of produced J/ψ in nuclear matter for relativistic heavy ion collisions is calculated. The absorption cross section σa.bs of J/ψ deduced in A-A collisions is considerably higher than that in h-A processes.The reason of obtaining this result different from former works is also discussed in terms of analysing the relation between and the initial interaction length.
An Re-entrant Cavity and Its Cathode Structure for the Thermionic Microwave Gun
Huang Yongzhang, Wu Gang
1994, 18(7): 658-663.
This paper introduces a single cell re-entrant cavity and its cathode structure used in the thermionic microwave gun. The essential parameters of the cavity are chosen according to the requirements of produced electron beam. We report design consideration on cavity shape, field distribution, resonant. frequency and coupling coefficient. Then we give the cold RF measurement results. The cavity is successfully used in the gun. Results of simulations is presented and is compared with measurements.
Beam Dynamics characteristic in 1/2+m Cell's Harmonic Microwave Cun
Zhao Zhentang, Lin Yuzheng, Wang Hongyuan
1994, 18(7): 664-672.
In order to decrease the energy spread and to get a small traverse emittance as well as high brightness of the electron beam in the injector of the FEL, a 1/2+m cell's microwave gun scheme adopted the technique of the harmonic cavity is presented. By using K. J. Kim method, the beam dynamics characteristic in the 1/2+m cell'S harmonic microwave gun is studied. The derived formulas demonstrate that with this scheme, the energy spread and traverse emittance of the electron beam are improved. In comparison with above analytical results, a beam dynamics simulation is performed with PARMELA code. The result shows that the harmonic microwave gun is favourable for improving the energy spread and repressing the phase space dilution.