1988 Vol. 12, No. 4
Display Method: |
A multi-state trapping model involving positron trapping at dislocations and jogs is proposed,in which the effect of positron detrapping can be omitted.According to this model the dislocations with variant jog density have different functions in positron Annihilation process.The case that dislocation trapping is predominant and the open-space ratio between dislocation core and single-vacancy were emphatically discussed.Using the data in some literature we have estimated the positron annihilated rate at dislocations and the jog interval on the dislocation line.The results obtained seems reasonable.
We constructed a MWPC prototype with effective area of 100×100mm2 and cathode strips.The distribution of induced charge on cathode plane and spatial resolution along the anode wires were measured by 55Fe X-ray of 5.9keV.The effect of readout number of strips used for the estimation of the centroid on spatial resolution were studied.Our results were compared with theoretical theoretical calculation.
The Doppler broadening of the two-photon annihilation line arising from the intermediate lifetime of positronium in a magnetic field has been measured using a time selecting γ-ray spectrometer.From the relation the kinetic energy and age.we have found that or thopositronium loses its energy rapidly between about 1eV and 0.25eV through inelastic collisions with SiO2 molecules and then is slowly thermalized through successive elastic collisions.It is also observed that the annihilation rate of the orthopositronium is larger while it has larger speed.The effect of the gradual thermalization of orthopositronium should be a main systematic error source,which was not understood,in the precision experiments on the decay rate of orthopositronium.
A nuclear emulsion stack bombarded by 200GeV/nucleon oxygen nuclei has been analyzed.The measurement of a ternary fragmentation event of a relativistic oxygen nucleus into three helium nuclei and 22 minimum ionizing particles has been performed.The mechanism of the fragmentation processes has been discussed.The fragmentation phenomena of the relativistic oxygen nuclei provied a direct experimental evidence for the cluster model of the oxygen nuclei.
Using the strong coupling expansion method in lattice gauge theory,we calculate the weak interaction matrix elements of │ΔS│=2.Our results of the KL-KS mass diference are not only consistent with those of meson mass spectrum obtained by the same method,but also close to the experimental value.
Based on the DPM model,the multiparticle productions in K-p and π-p soft-collisions are studied,the emphasis is put on fragmentation regions,The inclusive distributions in fragmentation regions and the forwardbackward correlation are calculated.It is pointed out that the asymmetry of distributions between K and p fragmentation regions may be used as a further test of the DPM model experimentally.
An analytical method is used to investigate the chiral symmetry restoring phase transition at finite temperature and density.The self-consistency equations for the order parameter at T=0 are generalized and the corresponding equations at finite temperature and density are established.The order parameter as a function of the temperature and the phase diagram are obtained.
The │ΔS│=1 weak interaction matrix elements of the nonleptonic K decays are calculated based on the strong coupling expansion method in lattice QCD.We compare our results with experiment,and show the enhancement of ΔI=1/2.
We discuss GUT including an extra Z0,while preserving the results of the standard model,and surmounting the difficulty of the proton decay.The increasing fermions are not bizarre Finally it is generalized to whole simple Li group.
The probabilities of overlappings of wave functions and of quark exchanges of a nucleon with its surrounding nucleons in nuclei are calculated.We obtain the deep inelastic 1-A structure functions which agree well with experimental data.An explanation on multiquark cluster model is given.Values of average radius of a nucleon in various nuclei are obtained and the model of swollen nucleon is explained."Quark conductivity"throught nucleus is predicted and "duality" of quark and hadron description is shown.
The antiproton-nucleus elastic scattering differential cross section of 12C,16,18O,40Ca and 208Pb at incident energies 50MeV and 180MeV have been calculated and analysed by optical potential.It is shown that the antiproton optical potential have strong absorption characteristics.It analyzing the optical potential parameters to best fit the experimented data,it is found that the diffuseness parameters could vary only in a narrow region and increased with heavier nuclei.These optical potential have shallow real parts.The absorption coefficients approach to zero inside the target nucleus,so that the elastic scattering takes place at the surface region of nucleus.
Large-angle elastic cross sections for the scattering of π+ and π－ from 16O at 114MeV are calculated using the first-order optical potential constructed from the α-particle model of 16O.The calculated results show that obvious improvement is obtained over the calculations employing the general first-order optical potential of the Kisslinger type.
In this paper the performance of a new type (modulating widths type)of linear periodic magnets is analysed.In ideal 2-dimensional case the field produced by this type of magnet is pure sinusoidal.Soft iron shield can be used to strengthen the magnetic field and in some cases the strengthening factor is larger than two.
The expressions of the field distributions in ideal case and in real case and the expression of strengthening factor are given.Methods for reducing undesirable harmonics in the magnetic field are also discussed in this paper.
The three-fold differential cross sections d3σ/dA dZ dE of the projectile-like fragment produced by 80.9MeV 16O on 27Al were measured by using the time of flight system with ΔE-E telescope.
The dissipation process and the nucleon transfer in this reaction have been discussed.
A new type of ionization chamber telescope is introduced which consists of two ionization chambers in series followed by a position sensitive semiconductor Si detector.The trajectory of the incident particles is parallel to the direction of the electric field in the ionization chamber.The advantages of this type of the detector are as follows:(1) its wide dynamical range allows the resolution for light particles as well as the heavy elements;(2) its good position resolution,makes it possible to cover a large solid (subtended about 14°) with a relatively smaller detector size.
The particle-number-conserving approach for treating nuclear pairing correlation is extended to treat the eigenvalue problem of the cranking hamiltonian.Detailed information about the seniority structure and the K-structure of the low-lying bands,and their spin alignments,signature splittings,and pair-transfer matrix elements can be provided in this formalism.
Using the numbers of excited particles and holes calculated by dissipative diabatic dynamics (DDD) as the initial exciton number n0,the energy spectra and angular distributions of emitted light particles for 40Ca+40Ca and 58Ni+58Ni at different bombarding energies are calculated based on the fast particle exciton model,compared with other models.
An exciton state density with angular momentum is derived in this paper based on statistical theory.The square of the spin-cut factor σn is proportional to the exciton number and the nuclear moment of inertia.When the exciton system closes to the statistical equilibrium,this exciton state density automatically approaches to the Fermi-gas nuclear level density with angular momentum.
Recently a new positive parity rotational band was observed,its moment of inertia is a bit larger than of ground,β and γ bands for some even-even nuclei of the actinide and rare-earth regions,and also was negative parity band.These facts can be interpreted by vibron model and octuple deformation.By a simple geometrical figure the more stretch of the polarized core was quantitatively estimated when there was α-cluster in the surface region of the core.If there is this polarized effect,it ought to be behaved in the angular distribution of α-decay.
A new continuous variable representation of the Elliott SU(3) model is given.Based on this representation,a novel approach——the extreme state eigen equation approach is proposed,by which all irreducible representation bases of SU(3) in canonical group chain have been obtained.By virtue of projection operation.the Elliott SU(3) irreducible bases are given.The physics and geometric meaning of this representation is discussed.
The concepts of internal transformation brackets of 4-body systems and quasi-Eular angle have been introduced in this paper.With their aid,the calculation of the 4-body hyperspherical transformation brackets can be greatly simplified by using those of the subsystems as building blocks.
A convenient block method used for high dimensional random triangle lattice has been applied to the monte carlo renormalization group study of Ising model on three-dimensional random triangle lattice.The critical exponents obtained are found to be consistent with all evact fractions conjectured from several approximate methods and experiments.
- A SCOAP3 participating journal - free Open Access publication for qualifying articles
- Average 24 days to first decision
- Fast-track publication for selected articles
- Subscriptions at over 3000 institutions worldwide
- Free English editing on all accepted articles
- The 2023 Chinese New Year-Office closure
- 2022 National holiday- office closure
- The 2022 summer holiday-Office closure
- Impact factor of Chinese Physics C is 2.944 in 2021
- The 2022 Labor Day Holiday-Office closure