## 1994 Vol. 18, No. 8

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**Abstract:**

Energy spectra of complex fragments emitted in the reactions of 46.7MeV/u

^{12}C with different targets

^{197}Au,

^{115}In and

^{58}Ni have been measured by telescopes，consisting of a gis ionization counter followed by a position Sensitive semiconductor detector.Tha most probable kinematical energies.E

_{p}of complex fragments and temperature parameters of long－live intermediate systems have been deduced by complex fragment ernergy spectra.The experimental values of E

_{p}are lower than the calculated ones by E=V

_{coul}+2T.The experimental values of complex fragment yields can be reproduced by simple A.Friedman statistical evaporation model satisfactorily.

**Abstract:**

The β-delayed α decay of

^{20}Na was restudied using neon target bombarded by 25 and 35.5 MeV protons.In this experiment a newly developed particle-telescope system including a gas ionization chamber as a thin ΔE detector was used. Two new peaks,one at 0.695 MeV and other at 0.907 MeV, were observed for the first time in the charged particle spectra. Based on particle identification, branching ratio and life time measurement,it is believed that these new peaks result from β-delayed low energy αdecay of

^{20}Na.The decay scheme and the low-lying level scheme of 20Na were thus revised.Its possible astrophysical implications were discussed.

**Abstract:**

Two methods are used to improve the L3 TEC resolution at track vertex.First,refit the lepton tracks by constrained curvature from high precision measurements on electron energy and muon momenta. Second, correct the average value of track offsets in each half sector of TEC.Combined methods improve the lepton track resolution at vertex from 137μm to 60μm.

**Abstract:**

An algorithm to construct the generator of gauge transformation for a constrained Hamiltonian system is given.The relationships among the coefficients connecting with first-class constraints in the generator is cleared.Based on the phase space generating functional,the corresponding Ward identities in canonical formalism is deduced.The preliminary applications of above results to a model in field theory which is functionally equivalent to the mixed Chern-Simons Lagrangian is discussed in detail.

**Abstract:**

This paper derives a set of basic relations about octet,decuplet and Singlet baryon production weights under two principles in mulliparticle production.From these relations,we give the origin of"spin suppression"phenomenon,and successfully explain why the singlet baryons have high multiplicities.

**Abstract:**

We discuss the naive lattice formulation of Chern-Simons theory, and quantize the simplest case using the Dirac quantization method for constrained system. We show that there is some singularity in the naive lattice theory,and find a way to avoid it.We also obtain the anyon creation operator.

**Abstract:**

Based on the SU(3)approximate symmetry in the strong interaction threebody and four-body semileptonic B-meson decays are analyzed.Relations between decay rates are derived.Some of these relations may provide information on the nature of various competing dynamical effects that can occur in semileptonic B-meson decays.

**Abstract:**

By utilizing the 1/N expansion technique,the d-boson energy εnd and the pairing interaction a0P+P are discussed for the sd Interacting Boson Model.Sm isotopes and 168Er are studied.The analytical results are compared with the published results calculated from the program PHINT.

**Abstract:**

Probability of cascade fission was studied within frame of statistical liquid-drop model and compared with result of ternary fission experiment,it increases with exited energy of compound nuclear system or mass of fission fragment increasing.

**Abstract:**

The neutron rich nucleus

^{11}Li is considered as a three-body system composed of

^{9}Li core and two outside neutrons.The coreneutron and neutron-neutron interactions are chosen to be of the attractive exponential potentials.The Shrdinger equation is solved by diagonalizing the Hamiltonian with the aid of the harmonic oscillator formalism. The structure of this system and the interparticle correlation are investigated by inspecting the shape-density and the neutron halo structure is obtained.

Hadronic Transport Model Explanation of K

^{+}/π^{+}Ratio in Relativistic Nucleus-nucleus Collisions**Abstract:**

We propose a simple hadronic transport model for investigating the K

^{+}/π

^{+}ratio in relativistic nucleus-nucleus collisions and point out that the thermal motion of baryons and multiple rescattering effect play an important role in the enhancement of K

^{+}/π

^{+}ratio.The experimental data of enhancement of K

^{+}/π

^{+}ratio could be explained within a reasonable temperature parameter (～150MeV).

**Abstract:**

The formula of β-stability line should be determined by the self-consistent calculations from the employed theoretical-framework.A slight difference formula of β-stability line from the traditional one is derived.A comment on the formula of β-stability line under Hartree-Fock approximation is given.

**Abstract:**

By using the folding model,the elastic scattering between two carbon heavy ions is studied in a wider energy range.The results show that the model gives a very good description of the experimental data.

**Abstract:**

A new measurement method of characteristic lifetime of positron annihilation in mercury cadmium telluride(MCT)in thermoequilibrium was proposed.A result of τ

_{b},the annihilation lifetime of positrons in bulk state in HgCdTe,being 277±1ps,and τ

_{d},the lifetime of positrons trapped in mercury vacancies,being 306±2pswas obtained.The result was discussed and compared with that from other methods.

**Abstract:**

The color-independent spin-orbit potential produced by the sea quark effect is introduced in the quark-quark spin-orbit interactions.The influences of the potential to the calculations of the baryon spectra and the baryon-baryon interaction are discussed qualitatively.

**Abstract:**

Beijing FEL facility has been built in IHEP,the saturated oscillation has been obtained at a wavelength of 10.68μm,on Dec.28,1993.The average output energy and the pulse width were measured respectively to be 3mJ,2μs.The corresponding osillation power is greater than 210kW,peak power is about 20MW, which is about 10

^{8}times higher than that of spontaneous emission. The FWHM of the FEL spectracal bandwidth is less than 2%.The small signal net gain is 24% per pass.The extraction efficiency is 0.45%.In the present experimental resules,BFEL can be saturated by changing electron energy at the wavelength range from 9-10μm,the maxmium average output energy and extraction efficiency are 10mJ,0.52% respectively,the minimum spectral bandwidth of 0.3% has achieved by shorting cavity length.

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

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

- Particle physics
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- Cosmology

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