1994 Vol. 18, No. Z1
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This paper describes in detail the procedures used in the identification of the new neutron-rich isotope 208Hg and the measurement of its half-life. The identification included two step chemical separations. The first step was the collection of Hg element products from the irradiated target with high efficiency and good element selectivity, which was realized by means of an off-line melt Pb target device. The second step was to extract periodically the growing Tl element from the collected Hg sample. In the γ spectra of the extracted Tl sample, a 2614.6 keV activity with a half-life of 3 minutes was observed, which may only be assigned to the daughter 208Tl of 208Hg decay.
By use of the maximum likelihood, a new method to fit space tracks with non-Gaussian measurement errors is introduced. Compared with the conventional least squares fit, the resolution has been greatly improved as does the reliability of distinguishing the false tracks.
The pseudorapidity distributions of charged particle multiplicity 4-24 produced in pp collision at 400GeV/c have been measured by using the LEBC films which were offered by the CERN NA27 Collaboration. The average maximum charged particle density in a selected pseudorapidity window (△η=0.5 or 0.1) rises linearly with the charged particle multiplicity. There is a trend for the probability distributions of the maximum particle density at large n to widen and flatten. But the event that the maximum particle density is anomalously high was not observed.
The excitation functions have been measured for the dissipative products in 19F+45Sc reaction from 102 MeV to 108 MeV in 300 keV steps at θl=26° and θl=42°. The thickness of the self-supporting 45Sc target is 53 μg/cm2. The energy coherence width T for each element measured is extracted and the corresponding dinuclear system lifetime is also deduced by the advanced Ericson statistical theory. The dissipative reaction mechanism is discussed.
By using super-Poincare tensor calculus, we construct an N=1 supergravity theory in 3-dimensions, and obtain the most general Lagrangian. The mechanism of spontaneous supersymmetry breaking and super-Higgs effect are studied in detail.
By means of the imaginary-time Green function method in the finite-temperature field theory, the coupling constant for interaction between η-meson and nucleons, the effective mass of η-meson and the dependence of single η-meson exchange potential on temperature are given herein in the case of pseudoscalar coupling and compared with results in the pseudovector coupling case.
The equation of state in the F-L model is calculated at the finite temperature and density. It turns out from the analysis of the isotherms of pressure versus net baryon number density that in the mean-field approximation, the deconfinement phase transition in the F-L model is of the first order.
In this paper, the space-time evolution of high energy heavy ion collision is described by the Relativistic Kinetic Equation. The rapidity distributions of the final state particles for 200A GeV 160 and 32S beams are analyzed in the central rapidity region. The relaxation times of various systems are determined.
A new characteristic variable, relative entropy R, is suggested to analyze the multiplicity distributions of particles produced in 14.6, 60 and 200A GeV 16O and 200A GeV 32S induced nuclear reactions. It is found that R appears approximately energy independent in the present energy region. The saturation of the rapidity-window dependence of R shows that the dominant part of created entropy is concentrated in the central rapidity region. Experimental data are in agreement with the prediction based on the FRITIOF of Lund model.
The forward-backward multiplicity correlations between various rapidity windows in high energy pp collisions are obtained by using Monte Carlo simulation based on a revised Three Fire Ball model with cluster mechanism taken into account. The results coincide with the experimental data of s=200, 546,900 GeV from UA5,which indicates that the model used is reasonable. It is shown that the effect of cluster mechanism makes forward-backward multiplicity correlation increase in short-range but decrease in long-range.
A variation method is developed to solve the Fokker-Planck (F-P) equation. One-dimensional fission probability is calculated and compared with other methods. The relation of the F-P equation and the Smoluchowski equation is discussed in light of this method, which paves the way to derive the multi-dimensional Smoluchowski equation with varying mass and viscosity and to solve more complicated equations.
In the usual relativistic mean field (RMF) calculation of stable nuclei, the tensor coupling of NNρ is not taken into account. It is necessary to clarify the contribution of the tensor coupling of the ρ meson when RMF is extended to nuclei far from the β stability line. The tensor coupling of the ρ meson is included and its effect is discussed in the present work.
Superdeformed bands of 193Tl are analyzed by means of the triaxial-particle-rotor model. Overall and excellent agreements between the calculated and observed spectra Eγ and the kinematic and dynamic moments of inertia J(1) and J(2) are obtained. The calculated B(M1) and dynamical quadrupole moments Q(1) and Q(2) are given. It is pointed out that the particle-rotor model can be used to analyzed the superdeformed bands in nuclei.
Within the framework of the Usdpf(16) interacting boson model, the effects of the octupole degree of freedom p- and f-bosons on the positive-parity states of even-even nuclei in rotational regions are discussed. It is shown that configurations of an even number of p-and f-bosons can not only be incorporated into the usual ground state band, β-, γ-vibrational bands, but also naturally form the Kπ=1+, 3+ rotation bands, etc.. This result is similar to that of the Usds(15)-IBM. The result is consistent with that of Usd-IBM. E2 transition probabilities are discussed briefly.
In this paper the general solution of the transient beam loading problem for a constant gradient travelling waye accelerator structure (SLAC-type structure) is obtained starting with the energy conservation law. In particular, for the thermionic microwave gun serving as a injector where the beam pulse current increases with time, the beam loading problem is treated firstly. Then, the solution is used to analyze the accelerator of Beijing Free Electron Laser and the result shows the beam energy decrease with the increase of the pulse current.
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