1989 Vol. 13, No. 6
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The elastic recoil detection (ERD) by using a 2.0—2.5MeV 4He ,ion beam has been employed to detect the depth profiling of hydrogen in the Silicon oxide and silicon nitride films.The correlation between the hydrogen content and the deposition condition is given.Maximum probing depth,detection limit and depth resolution are discussed under our experiment conditions.
The three photon decay of positronium was further studied using positronium source composed of 22Na and silica aerogel and triple fast coincidence method.We measured the angular distribution of the photons in the large angle region under symmetrical geometry with respect to the third photon.The whole curve of the angular distribution of photons was given combining with the data in the small angle region which was published before.The results were in good agreement with theoretical predicted values.
The potential distribution in the electrostatic decelerating lens is calculated with charge-density method.The Gill method is used to simulate the electron orbits.The resolution of the analyzer is 1.0eV at 20keV.The influence of the beam diameter,injection angle and the hole diameter of the third electrode to the resolution are discussed.Some additions to the experimental data are given by simulation.
Using the Mellin transformation,we get the analytical series expression for the gluon distribution function from Altarelli-Parisi equation.This series converges rapidly.The behaviour of the gluon distribution function is also discussed from this expression.
The Hilbert space and the representation of the generators of Virasoro algebra for bosonic string under a holomorphic polarization are given in this paper,It is shown that the contre term of Virasoro algebra may be interpreted as curvature of a holomorphic vector bundle (holomorphic Fock bundle) on coset space G11=G/H where G denotes the conformal transformation group and H the one-parameter subgroup generated by the generator L0.The condition of the conformal anomaly cancellation may be expressed as the vanishing curvature of the bundle which is obtained by the product of the holomorphic Fock bundle and the holomorphic ghost vacuum bundle.The geometric interpretations of both classical and quantized BRST operators,ghost and antighost operators are also discussed.
An improved Monte Carlo scheme is applied to the computation of the expectation values of nxm Wilson loops in both 2-and 3-dimensional SU(2) lattice gauge theories.The results are compared with those simulated by the discrete group Y120 and the exact results in two dimensions.
We extend our model by introducing explicitly the energy-momentum of quarks.By using the Monte-Carlo method,the rapidity distribution in light jet events is calculated.Agreement with experiment data is good.The baryon-antibaryon correlations in rapidity,open angle,azimuthal angle are also given,which are in agreement with experiment on the whole.
The canonical system of O(3) nonlinear sigma model in 1+1 dimensions is studied in this paper.It is shown that the topological term in the model will disappear under a suitable canonical transformation for the system.The significance of this result is discussed.
The effective two-meson-exchange potential with regard to the box diagram in the N-N interaction has been derived by virtue of the one-gluon-exchange quark-antiquark pair creation model.The result shows that the general feature of this effective potential agrees with that of the phenomenological σ-meson exchange potential in coordinate space.
We propose a hybrid quark hadron model to describe high energy composite particle scattering.The parameters for quark sector in the model are determined by fitting pp scattering data.We apply the model without any free parameter to proton-alpha elastic scattering.Our model yields a quite large improvement over various calculations done before and provides a very good agreement with existing data available.Our results also show that the quark degrees of freedom in NN interaction play an important role in improving theoretical description of experimental data and must be included in future calculations.
Elastic antiproton-nucleus scattering is analysed by a phenomenological optical model potential with spin orbit interaction.The elastic scattering differential cross section dσ/dΩ,polarization P(θ) and spin rotation function Q(θ) can be discribed by this potential.From the comparison with 12C nucleus experiment data of differential cross section and polarization,we obtain a more realistic antiproton optical potential.
The properties of isovector giant resonances are discussed with the help of the nuclear ground state density profiles obtained from self consiotent semi-classical calculation.Both the component with ΔT3=0 and the components with ΔT3=±1 are considered.The isospin properties of the giant resonances are thereby studied.The results are in good agreement with HF-RPA calculation and experimental evidences.
A modified microscopic model for calculating the total reaction cross section in the intermediate energy domain is given,the effects of neutron skin,ground state deformation and surface diffusion of the nuclear matter distribution is discussed quantitatively.The experimental data and the calculated results show that the surface diffusion of the nuclear matter distribution which was assumd to be dependent on the neutron excess is a important factor for the rapid increase of the total reaction cross section induced by neutron-rich nuclei.
The photonuclear reaction cross sections of giant dipole resonances for 208Pb,186W,181Ta,175Lu,75As and 55Mn are calculated by using the extended exciton model in a further approximation.They are in good agreement with experimental data.The theoretical framework being given in our previous paper is reasonably supported.
The signature-splitting of the energies,B(M1)-values and dynamical quadrupole moments in 159Tm are investigated by means of the extended particle-rotor model.In particular,the effect of second-order Coriolis interaction on the signature-dependence of B(M1)-values is discussed.It was noted that the calculated values are in qualitative agreement with the measured data.
We have introduced the photon angular distribution for moments of the process e+e－→J/ψ→γB,B→P1P2P3 to discuss the ι-E puzzle and got an effective criterion to distinguish whether there exist E(1++) component in the peak for the process e+e－→J/ψ→γKKπ.
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