## 2000 Vol. 24, No. 2

Display Method: |

**Abstract:**

Using Leznov-Saveliev algebraic analysis and Drinfeld-Sokolov construction,we obtaine the explicit solutions to the super Liouville system in super covariant form and component form. The explicit solution in component form reduces naturally into the Egnchi-Hanson instanton solution of the usual Liouville equation if all the grassmann odd componenets are set equal to zero.

**Abstract:**

From the generalized Yang-Baxter relations RLL=LLR

^{*},where R and R

^{*}are the dynamical R matrix of A

^{(1)}

_{n-1}type face model with the elliptic module shifted by the center of the algebra, using the Ding-Frenkel correspondence, we obtain the Drinfeld currents of algebra A

_{q,p,π}(gl

_{n}).

**Abstract:**

Based on the configuration-space generating functional obtained by using the Faddeev-Popov trick for a gauge-invariant system and phase- space generating functional obtained by using the Faddeev-Senjanovic method for a constrained Hamiltonian system with a singular higher order Lagrangian respectively, the conservation laws at the quantum level were derived. A preliminary application of the present formulation to the higher-order Maxwell non-Abelian Chern-Sinons(CS) theory is given,the quantal BRS conserved charge and quantal angular momentum for higher-order Maxwell non-Abelian CS term coupled to scalar fields were obtained. The results arising from configuration space generating functional coincide with the result deriving from phase-space generating functional,and the quantal conserved angular momentum differ from the classical one in that one needs to take into account the contribution of the the angular momentum of ghost fields in Maxwell non-Abelian CS theories. The fractional spin property for CS theories is discussed.

**Abstract:**

The correlation function method is applied to analyze the fluctuation of the excitation function in the dissipative nuclear reaction. By deriving the energy autocorrelation function, angle correlation function, elements correlation function and isotopic element correlation the characters of the nuclear reaction system in the dissipative reaction varying from the equilibrium to the non equilibrium system are analyzed, and the special role of these method in the study of the dissipative nuclear reactions shown. Experiments of 4.5MeV/u

^{27}Al+

^{27}Al and 102.5MeV

^{19}F+

^{51}V are analyzed by using these function derived in this articles, and the information in dissipative nuclear system, which can be drawn out from this method, is pointed out.

**Abstract:**

The excitation function was measured from θ

_{lab}=10.4° to 57.4° in dissipative collision

^{27}Al+

^{27}Al with incident energy ranging from 114 to 123 MeV in step of 200 keV. The Angular-cross Correlation Functions (ACFs) of cross section fluctuation within large angle region were obtained through experiment for the first time. It is found that the angular coherent width is at least 40°. It is interesting that the ACFs is not simple bell shape but shows strong asymmetry. The over-all behavior is that ACF varies more quickly for the backward angles. Itis also noticed that the cross section fluctuation in the forward angle region (θ

_{cm}<70°) shows much stronger angular coherence than in the backward angle region (θ

_{cm}>70°). This angular dependence may be attributed to the coherent rotation effect of intermediate dinuclear system.

**Abstract:**

The degradation of Λ transverse polarization produced in S+Pb central collisions at energy 200 GeV per nucleon has been studied in detail. The S+Pb central collision events have been generated using Monte-Carlo generator——LUCIAE at 200 GeV per nucleon. The various factors degrading Λ transverse polarization have been analysed quantitatively. The ratios of Λ′s produced from rescattering, secondary production and decays of Σ, Ξ hyperons to the total measurable Λ′s in experiment have been investigeted and the degradation effect of these Λ on the total polarization has been determined. The simulation and calculation show that above three factors decrease the Λ transverse polarization strongly, however, can not eliminate the polarization completely when the Λ′s are assumed to be produced from hadronic gas in the final state. To explan the experimental data of vanished Λ polarization, it probably needs to consider new mechanisms of Λ production, including a weak effect of QGP formation.

**Abstract:**

Based on the next leading order (NLO) perturbative QCD calculation and adopted parton distribution functions from double Q

^{2}rescaling model (DQ

^{2}RM) in nuclei, we have discussed the variation of K-factors in p N(A) Drell-Yan process. Our results show that K-factors could not be treated as constants as usual, but are varied markedly with the kinimatic variable x

_{T(A)}. In the ISR and SppS energy regions, when 2×10

^{－3}≤ x

_{T(A)}<1, K-factors decrease markedly as x

_{T(A)}becomes smaller, but after x

_{T(A)}<2×10

^{－3}, Their values increase rapidly as x

_{T(A)}further decrease. K-factor has a little dependence on nucleon number A of a nuclei also, and their effects are more clear in small x

_{T(A)}region. These observations are important for stringent test of some models and some physical quanties with Drell-Yan (Drell-Yan like) process in super high energy regions.

**Abstract:**

According to the SU(3)

_{rf}×SU(2)

_{s}×SU(3)

_{c}group classification theory,the total antisymmetric baryon wave functions are constracted, in which the mass difference between s quark and light (u,d) quark are considered. A comparison with the case of no mass difference between s and u,d quark is made. It is shown that the mass difference effect is not negligible in the interaction energy matrix elements.

**Abstract:**

The interaction energies of the last i proton(s) and the last j neutron(s) were obtained from nuclear mass-data-base. The last n-p interaction energy ε

_{1p-1n}of odd-odd nuclei was compared with half of the average value of the last proton-dineutron interaction energy ε

_{1p-2n}in odd-Z nuclei and the last diproton neutron interaction energy ε

_{2p-1n}in odd-N nuclei. It is found that the former is systematically greater than the latter. The enhancement of n-p interaction may be attributed to the effect of pairing weakening the n-p interaction in odd-A nuclei as well as GM shifts. Additionally, it is found that ε

_{1p-2n}in odd-Z nuclei is generally approximate to ε

_{2p-1n}in odd-N nuclei with the same mass number A, which is equivalent to the Garvey-Kelson mass relation.

**Abstract:**

Within the framework of an isospin-dependent quantum molecular dynamics model which includes isospin-dependent symmetry energy, Coulomb energy, nucleon-nucleon cross sections, Pauli blocking, and initialization, we have shown that there is a strong isospin dependence of the radial expansion flow from the symmetric central collisions at incident energies of a few hundred MeV per nucleon. It is found that the more neutron-rich system exhibits smaller radial expansion flow, which is shown to result from the isospin dependence of nucleon-nucleon cross sections and to be independent of the nuclear symmetry energy. It suggests that the experimental measurement of the radial expansion flow for reaction systems with different ratios of neutron to proton provide a novel method for determining the isospin dependent in-medium nucleon-nucleon cross sections.

**Abstract:**

The multi-photon correction function for the single photon time measurement in scintillation crystals is computed. The influence of this fuction on the measured decay time is studied. A correction formula for measured time spectrum is presented.

**Abstract:**

Based on the interaction of γ-ray with NaI(Tl) crystal and the transportation of luminescence photons produced in the crystal, a simulation model has been setup using the GEANT3 codes for a small Gamma Camera with a planar NaI(Tl) crystal coupled to a position sensitive photomultiplier (Hamamatsu R2486-05). The results demonstrate that the image is significantly shrunk from the circumference to the center because of the asymmetry of the spacial distribution of the photoelectrons. The quantity of shrinkage depends on the thickness of both the crystal and glass window. Treatment of the edge surface of the crystal is very sensitive to the shrinkage of image. Suggestions for suppressing the image shrinkage are presented.

**Abstract:**

Broad band continuous and high intensity coherent synchrotron radiation (SR) emitted from the 4ps electron bunches provided by the 30MeV linac of BFEL setup is analyzed and numerically calculated. High intensity coherent SRs in the mm-wave region and in the far IR to mm-wave region can be obtained respectively by directly using these bunches and by compressing their pulse widths to 1ps or sub ps. The later as a coherent source of radiation is of high value in applications because it is within the wavelength region where the coherent radiation source is lacked. The CSR power is enhanced by a factor of 10

^{8}—10

^{9},approximately the number of electrons per bunch, compared to incoherent SR. The coherent SR power is within hundreds micro-watts to milli-watts dependent upon the chosen wavelength and gathering angle regions. Experimental designs on CSR generation and bunch length measurement are presented.

**Abstract:**

The staggering phenomenon of the superdeformed bands

^{149}Gd(1),

^{148}Gd(6) and

^{148}Eu(1) is analyzed with a SU

_{q}(2) rotational spectroscopy expression. When the spin of the head of band is chosen properly,the calculating bifurcation of ΔI=4 is agreement with that extracted from experiment.

**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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