1999 Vol. 23, No. 07
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High spin states of 84Sr were populated by bombarding, 70Zn target with 75MeV 18O beam provided by HI-13 Tandem Accelerator of CIAE. γ-γ coincidences and DCO ratios were measured using eight anticompton Ge detectors and one planar. A new level scheme of 84Sr was established in which 12 new energy states and nearly 30 new γ-transitions were identified in present work. Level scheme was compared with its even-even isotopes 78,80,82,86Sr. It shows that 84Sr is a transitional nucleus, namely its ground state band exhibits a collective nature. The negative bands were extended to spin of 19－ and the γ-transition energies take on the nature of stagger. The negative band levels are in good agreement with D.C.M. theory caculations.
The accuracy of neutral track measurement by Barrel Shower Counter (BSC) at BES is inveshgated. The photon energy in BSC is corrected using radiative Bhabha events and the error is determined. The error of photon position in BSC is also determined using the e+e－ process. All these results can be applied to BES analysis including neutral tracks, and the systematic error can be remarkably reduced when the kinematic fit is adopted.
A new method used to discriminate neutrons and photons in liquid scintillators with charge comparison and using a CAMAC-microcomputer data acquisition system is described. The total charge and multi-channel partial charges for different time segments of pulses from liquid scintillator samples of NE213 or BC519 radiated by 241Am-Be or 252Cf neutron sources are measured. The dependences of n,γ seperation in scintillators on delay time and energy distribution are given from off-line data analysis. The energy distribution of neutrons or γ-ray and pulse shapes for fast and slow components of scintillators can be measured using such a n, γ discrimination method.
The distribution of induced charge of MWPC's W-S cathode was calculated in detail. A 100×100mm2 MWPC prototype with W-S cathode was made. The localization resolution of MWPC was measured with 55Fe X ray and the two-dimension image of incident X ray was obtained.
A CsI(T1) detector with a two-dimension posihonal sensitive photomultiplier readout at Radioactive Ion Beam Line in Lanzhou (RIBLL) is reported. The Cs(T1) scitillator is 10 mm in thickness and 60mm×60mm in active area. Its spatial resolution of 0.81mm (FWHM) is achieved. Finally the Monte-Carlo method is employed to simulate its spatial resolution whose result is in good agreement with the tested.
In this paper, the one-loop contributions to the rare B-decays B→Xs,dνν and Bs,d→1+1－(1= e,μ,τ) from the charged pesudo-Goldstone bosons P± and P±8 are calculated. Within the parameter space, we find that: (a) the P± and P8± can provide rather large enhancements to the branching ratios of the rare B-decays in question, the maximum increase is about a factor of 3 to Br(B→Xs,d,νν), and a factor of 5 to Br (Bs,d→1+1－); (b) the color-octet pesudo-Goldstone boson P±8 dominates the contributions to all rare B-decays under consideration; (c) no limit on the masses of charged pesudo-Goldstone bosons can be achieved from the current experimental data, but the forthcoming data may reach the sensitivity to find the signals of new physics beyond the Standard Model.
The vector meson mass in 1+1 dimensional lattice QCD is calculated by using the variational method. The predictions are proved: The errors which come from the finite lattice spacing can be greatly reduced evidently by improving the lattice Hamiltonian with Wilson quark.
Using supersymmetric quantum mechanics, serveral new classes of condihonally exactly solvable potentials are constructed from the displaced non-harmonic oscillator potential. And the corresponding nonlinear spectrum-generating algebras are obtained.
A Bosonic string model at finite temperature on the gravition gμv and the dilaton φ background field is examined. Moreover, the duality relation of energy momentum tensor on high genus Riemann surface is derived. At the same time, the temperature duality invariance for the action of string gas matter is proved in 4-D Robertson-Walker metric, the string cosmological solutions and tomperature duality of the equations of motion for genus g=1 and 2 are also investigated.
We derive the non-local two-gluon vacuum expectation value with translational invariance in Lorentz gauge. By means of the obtained two-gluon vacuum expectation value, the lowest dimentional nonperturbative QCD corrections to one gluon exchange quark-quark, quark-antiquark and qq pairexcitation potentials are given.
In this paper, the fomulations of the energy density and pressure density of nuclear matter are derived in detail in one loop approximation in the relativistic σ-ω model. The changing of the binding energy and pressure with density is calculated numerically, and the pressure density is calculated in thermodynamics and hydrodynamics respechvely. We conclude that the pressure density in these two formalisms are similar.
The mechanisms of the energy degradation of leading particle, of the effechve dissociation of CC pair (the precursor of physical J/ψ) in the colour electric field of strings, and of the hadronic absorption (both baryon and meson) are introduced into the proposed hadron and string cascade model, JPCIAE. That has been used to calculate the J/ψ suppression factors in pA, AB (with light projectile), and Pb+Pb collisions at 200 A GeV/c energy. The theorehcal results reproduce simultaneously both the cormsponding NA38 and NA50 data fairly well, which arises the queshon of whther there art J/ψ anomalous suppressions in 158 A GeV/c Pb+Pb collisions.
In this paper, besides including u,d,s quarks and their anti-quarks the charm quarks and their anti-quarks (cc) were still included in the calculation of flavour kinetics of quarks. Using relativitic hydrodynamics model with the effect of quark flavor kinetics, invariable mass dilepton spectrum of M≤4GeV/c2 has been calculated. The dileptons are eastted from Phase transihon process of an expansion quark matter which is created in collisions of 238U+238U at energy～200GeV/u. The numerical results have been compared with experimental dare of CERN SPS qualitatively. A prelimings conclusion has been given: quark fragmentation and effect of flavour kinetics are the causes of suppression of the peak of J/ψ→μ++μ－.
Using three methods (the best-fit method, the graphic method and the bandhead moments of inertia J0 systematics), the spin assignments of the available superdeformed bands observed in A≈190 region have been analyzed systemahcally. The spins of most (～70) SD bands have been assigned reliably and consistent with the experimental values. The J0 systematics are inveshgated in detail.
Based on Haissinsky equation, some study results of the effect of narrow-band impedance on logitudinal static distribution of bunch are presented. The study is carried out with analytic method and simulative method.
A 14.5 GHz ECR (Electron Cyclotron Resonance) ion source with high charge stato and high magnetic field was designed and built. The structure characteristics, optimization design of parameters and magnetic field distribution are described, and the commissioning results are given. The maximum axial magnetic field on the axis is 1.5 Tesla. The hexapole field on the chamber surface is 1.0 Tesla. After initial commissioning, the ion source can produce typically 07+140 eA, Ar11+185eA and Xe26+ 50 eA. The results from this new ion source are compared with the best ECR ion sources over the world in 1998.
Wavelength dispersive posihon sensitive spectrometer(PSS)with a flaterystal is a new type of high energy resolution equipment for analyzing X rays. It can be used in study of elemental analysis, chemical states and atomic physics. The paper describes the performance of PSS developed by us as well as the principle of PSS and its core part-position sensitive proportional counter. The energy resolution of 25eV, 15eV and 7eV have been obtained for 55Fe, Ti and Si, respectively, using developed PSS. Such resolution can meet the requirement in elements analyses.
The dark matter in Universe, its class and candidates, and the significance of observation are briefly described. The methods and results and its progress of detection for the cold dark matter particles are reviewed, in particular, the observation of DAMA collab. (Beijing-Rome) gives the new limit on WIMP search and the firstannual modulation signature:
it is shown that an event sample from the Monte Carlo simulation of a random cascading α model with fixed dynamical fiuctuation strength is intermittent but not chaotic, while the variance of dynamical fluctuation strength in different events will result in both the intermittency and the chaohcity behavior. This shows that fractality and chaoticity are two connected but different features of non-linear dynamics in high energy collisions.
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