1995 Vol. 19, No. 5
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The τ+τ－ production has been studied in the data acquired by the Beijing Spectrometer (BES) at the comer-of-mass energy 4.03 GeV. Using a double-tagging technique, the decay τ~±→π~+π~-π~±υ_τhas been investigated. The branching ratios are determined to be Br(τ~±→a_1~±υ_τ→ρ~0π~±υ_τ, ρ~0→π~+π~-) = (7.3±0.5) % and Br(τ~±→ K~*±υτ→K_s~0π~±υτ, K_s~0→π~+π~-) = (6.0 ±1.5) ×10~(-3). From the Dalitz projection distribution, the dominant decay mode of ρπ in a~1 decay has been observed. Meanwhile,we have also found that the S-wave contribution dominates the a_1 decay. Applying the Kuhn model to fit the data, we have obtained the a_1 resonance parameters of m_a1=1.24±0.02 GeV and Γ_a1=0.57±0.07 GeV.
Two particle correlations at small relative momenta have been measured for 40Ar induced reactions on 197Au at E/A=25MeV. The relative populations of states of 4He and 8Be were extracted from p-t and α-α correlation functions, respectively.The temperature of MeV was obtained from relative populations of 8Be states by correcting sequential decay carefully, and the temperature of T=3.6±0.4MeV was deduced by modifying with 30 percent of sequential decay on 4He ground state.
Using the method of an eiginvalue equation truncated according to the continuum limit, we calculate the vacuum state of 2+1-dimensional SU(3) lattice gauge theory. The results are consistent with those computed through strong-coupling series in the strong coupling region, and display satisfactory scaling behavior in the weak coupling region.
The canonical Ward identities for a system with singular higher-order Lagrangian are derived and some application to the gelleralized QCD are given. The new relations of the Ward identities for gauge ghost field proper venices are obtained which differ from the usual Ward-Takahashi identities arising from BRS invariance. The expressions for PCAC and generalized PCAC of AVV venices are also obtained.
The removability of the topological term in 2+1 Dimensional CP1 model is studied. Both the classical canonical transformation and quantum unitary transformation for the removal of the topological term are obtained. It is pointed out that,in order to give an answer to the question of whether the topological term exists or not, one has to study not only the corresponding microscopic spin model but also the vacuum structure of the CP1 model.
The Holstein-Primakoff realization and the Nodvik realization for a two-parameter deformed quantum algebra SUqs(2) are constructed, and the deformed maps of a quantum algebra SUqs(2) and a two-parameter deformed harmonic oscillator are given.
The further classifications of JT coupled states for nucleons by the Casimir operator C of R(5) group have been calculated. The multiplicities of JTC classification (which depends on both J and T) have been factorized into one factor depending on J and T, and the results for j≤7/2 are listed. Tollowing the irredicible representation of R(5), the siniority v and reduced isotopic spin τ can be used to simplify the calculation of matrix elements of any tensor operator by the selection rules of υ and τ.
A modified effective quark-quark interaction, which include the exchange of four kinds of field, is derived from the chiral symmetry requirement. By using this modified quark-quark interaction, the 3S1 and 1S0 phase shifts of N-N scattering is studied in a RGM framework. Both the 1S0 and 3S1 phase shifts are in good agreement with the experimental data, especially the 1S0 phase shifts are improved a lot compared with the former calculations.
The physical quantities such as energy difference δEI of the positive and negative parity states of the same spin, moment of inertia J(1) and J(2), electric dipole transition branching ratios of first negative parity states and the relations between them and angular momentum or rotational frequency ω and mass number A are obtained from the experimental data. So the intrinsic structure and dynamics of negative parity states can be deduced.
Deformation consisting of a series of quasi-Cassinian rotating bodies surrounding a inner joined sphere is assumed to be that associated with symmetric multifold fissions into two or more fragments. The deformation shapes with only one parameter evolve smoothly from that of an initial spherical nucleus to the scission point. The shapes are calculated using a quasi-Cassinian ovaloid shape parameterization, which has been demonstrated to be a good approximation for binary fission.Using this parameterization the deformation potential and barriers in 2,3,4,6 and 8-fold multifold fissions are calculated. Proximity effects are included. The temperature dependence of these fission barriers is considered too. Finally the fission dynamics delay effects on the multi-fission processes is also discussed.
The equations of motion for multi-time correlation Green's functions have been transformed into those for equal-time correlation Green's functions, which include the equations of motion for quark's and gluon's density matrices as well as vertex functions.In two-body correlation truncation approximation, we present the formalism for the equations of motion, Gauss law and Ward identies explicitly.
The shape of the emittance contour of a charged particle beam can be described by the contour function. In this paper the variance of the beam contour in the nonlinear transport system is studied by means of the contour function theory and Lie algebra. Its inverse problem, the selection of parameters of the transport system according to the beam properties, can be studied also. As examples, the improvement of the beam quality by means of the nonlinear element and the beam matching in the nonlinear periodic field system are discussed.
This paper describes experimental apparatus and performance of the X-ray diffraction station at Beijing Synchrotron Radiation Facility (BSKF). Using a SR source of BEPC and the X-ray diffractometer, the study of multilayers and semiconductor superlattice structure, as well as the measurements of residual stress relaxation anddistribution around the ceramic-metal (Si3N4/Steel) interface have been developed.
A new heavy neutron-rich isotope 239Pa has been observed for the. first time in the interaction of 50MeV/u 18O with natU targets. Protactinium products were separated radiochemically from the complex mixture of the reaction products. The results observed from the decay of 239Pa and its daughter 239U show that a new heavy neutron-rich isotope 239Pa was produced and identified. The measured half-life is 106±30 min.
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