## 1992 Vol. 16, No. 7

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**Abstract:**

A method for the measurement of the vacuum decay rate λ

_{0}of orthopositronium is suggested and the preliminary result is obtained λ

_{0}=7.034±0.013μs

^{－1}.The possibility for the improvement of the experiment has been discussed.

**Abstract:**

Calculation has been made when we adjust 4W1B beam line in Beijing Synchrotron Radiation Facility.The relation among the intensity,energg dispersion,energy accuracy of the monochromatic beam and all adjustable freedoms is acquired.The reasonable procedure and the precision requirement of adjustment for each freedom are given.

**Abstract:**

We study the phase transition in Z(N) Pots spin model by an analytical approach—the generalized cumulant expansion with mean field approximation.As a test,we perform the expansion to the third order correction for Z(3),Z(4),Z(5) and Z(60 cases.The critical points turn out to be closer to the exact values when higher corrections are taken into account.

**Abstract:**

For a gauge theory of self-dual fields,whose S-matrix element manifestly including the self-duality constraint is obtained by using the path integral light-cone quantization.

**Abstract:**

In this paper.based on the FL-non-topological soliton model,we discussed the possibility of the formation of the FL-soliton star and its behavior at high temperature.We find that the stable,cold and spherical FL-soliton star can be formed,under the necessary condition W>3B.At high temperature,the FL-soliton bag disappears by the phase transition,but there may be some stellar configuration.

**Abstract:**

Using the free field representation,we calculate,the r-matrix and classical exchange algebra for WZNW model under periodic boundary condition,and discuss the quantum counterparts of the exchange algebra as well as the performances of the r-matrix and classical exchange algebra under Hamiltonian reductions.

**Abstract:**

The saturating chiral breaking field theory are used to study the compressibility of the Fermi-liquid and the excitation energies of the giant monopole and quadrupole states in the framework of mean-field theory.It is found that the compressibility of the Fermi-liquid in the nuclear system,and the excitation energies of the giant monopole and quadrupole states are more close to the experimental values in comparison with the results of the σ-ω model.

**Abstract:**

Based on Drell-Yan Mechanism modified by pertubative QCD and taking account of the contribution of vector meson states,we analyzed and explained the data of the WA-78 group ni (π

^{－},P)+A→μμ+X process at 2m

_{μ}

_{A}(x,Q

^{2}) in 1-A deep inelastic scattering process at 0.0035

^{2}/c

^{2}.In our analysis,after comparison with the data of the CIP group for the same process but at different m

_{ll}and x

_{F}regions,we gave a good explanation for why the influence of nuclear target displays a strong shadowing effect in former case while a strong antishadowing effect in latter case.By the rescaling model and other reasonable assumptions,we showed it is intimately connected with the above mentioned the R

_{A}(x,Q

^{2}) and thus further revealing the essential connection for the influence.

**Abstract:**

Fluctuations of the produced particles of the final states in high energy collisions may be the break through for investigating multi-particle dynamics.How to eliminate the statistical noise of the system is one of the most important problems.In this paper the influence of the statistical noise on fractal structure is analysed and a kind of method for eliminating statistical noise is proposed by using the Monte Carlo simulation based on a simplt dynamical model.

**Abstract:**

The complete fusion excitation function for the

^{16}O+

^{28}Si reaction is measured in the range of 50—90MeV with step of 1.0MeV.It is analysed by using some theoretical models and the model parameters are extracted from this analysis.Gross structure is found in the excitation function when E

_{CM}<46MeV.The energies of peaks are 34.5,38.5 and 43.0MeV,respectively.The structure vanishes gradually when E

_{CM}>46.0MeV.

**Abstract:**

The proton-rich isotope

^{65}As was observed preliminarily by 20.11A MeV

^{64}Zn beam bombardment on a 17.2mg/cm

^{2}Be target.The detecting system comprising a magnetic facility RIPS,a PPAC,an ionization chamber,and a PSSD was used to identify the charge states,atomic numbers,and masses of the reaction products.

**Abstract:**

A symmetry ternary fission (STF) shape with a spherical residue plus 3 rose-leaf-like rotating bodies (SRRL) has been proposed to describe the large deformation process from sphere to scission point with one deformation paramenter.By LDM,the relative Coulomb and surface potential with sharp surface have been calculated; as a example in several nuclei we present STF collective potentials,from which the shape and barrier height in saddle point and TKE determined by coulomb energy in scission are given.Also the shift of C.M.for each prefragment in STF process and the deformation energy for new born fragment are obtained.Considering the dependence of nuclear surface tension on nuclear temperature,the STF barrier height for hot nuclei would be decreased and then the STF probabilities over the barrier would increase too.The calculated results in the SRRL have been compared with previous results by oblate shape model.

**Abstract:**

The dynamical process of heavy ion collisions in the energy region of 10 to 100MeV/A has been investigated by Quantum Molecular Dynamics model.According to the calculated mass distribution of clusters,the time evolution of mass distribution and density distribution,the reaction mechanism and its characteristic are predicted and compared with those obtained from the BUU model.

**Abstract:**

With Hartree-Fock approximation,the relation between excitation energy and temperature has been obtained and discussed for both infinite nuclear matter and finite nucleus Pb

^{208.}

**Abstract:**

By analysing specific examples,it is shown that the Schwarzchild solution and the Booth's solution are a genus of solutions in space-time of arbitrary spatial dimension.

**ISSN** 1674-1137 **CN** 11-5641/O4

Original research articles, Ietters and reviews Covering theory and experiments in the fieids of

- Particle physics
- Nuclear physics
- Particle and nuclear astrophysics
- Cosmology

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