1992 Vol. 16, No. 11
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The formation yield of positronium (Ps) as a function of target temperature has been measured when positron implanting energy was 20eV.By thermal dynamic analyising we obtained the binding energy Eb of positron surface state of germanium to be 2.2eV and the thermal activation energy Ea of Ps to be 0.2±0.01eV at vacuum 1.33×10－4Pa.The different of Eb and Ea at the condition of high and ultra-high vacuum was discussed.
This paper reports the design and construction of the primary beam of the test beam on BEPC,as well as the acquirement of the positive-charged secondary beam,and the various particles,e+,π+,μ+,p,in the secondary beam have been measured with TOF method and threshold Cherenkov counter.The radiation damage studies of SDC calorimeter modules using the test beam have also been briefly described.
We constructed the factorizable S-matrix and obtained the symmetry operator which commutes with the S-matrix and has a new form of "coproduct",the elements of which depend on the parameters defining the toroidal rapidity surface.By defining a new operator which commutes with the symmetry operator the Yang-Baxter equation can be obtained.Finally,the relation between the broken ZN symmetric model and the chiral Potts model was expressed explicitly in the selfdual genus zero limit.
The limiting fragmentation behaviour of the single-particle pseudo-rapidity distributions and the two-particle correlations in oxygen-nucleus induced interactions in the energy region from 3.7 to 200A GeV is systematically investigated,and that of the dynamical fluctuations of multi-particle distribution is studied by using the relation between the factorial-moments and the multi-particle pseudo-rapidity distributions.
Starting from the experimental data on the dependence of intermittency phenomena on various physical parameters,it is shown that the average transverse momentum per event plays a decisive role in determining the intermittency strength.This means that intermittency phenomena is closely related to the super-soft processes,observed experimentally in recent years.
As two skyrmions overlap,a molecular-like binding may arise.This may be one of the main sources of missing intermediate range attraction in NN interaction.The attraction is found to be strong enough to form bound state of two nucleons.It seems then that one no longer needs to introduce phenomenologically scalar meson which has never been observed.
By means of the quark-antiquark pair creation model via one-gluon exchange,the effective interaction among quark,which is equivalent to the meson exchange intervening between two hadrons,is discussed.It is shown that this process includes interactions not only between two quark,but also among three quark.Obviously,such effective interaction is more general than one gluon exchange potential (OGEP).
The energy spectra and angular distribution of α particles emitted from 12C induced reactions with 58Ni,115In and 197Au have been measured.Three moving sources of emitting α particle are clearly seen from invariant cross section distribution in velocity coordinates.The experimental data were analyzed by using three moving sources.Extracted parameters of the source with half-beam velocity are in agreement with the systematic values from Fermi Gas Model.The energy spectra and the extracted parameters for various targets are discussed.The low energy peak in energy spectra is possibly from the emitted α particle from equilibrium system after pre-equilibrium emission of target-like products.The energetic α particles are mainly from projectile fragmentation and projectile-like fragmentation.
A detector telescope consisting of a BaF2 crystal and Si detectors is used to measure forwardly emitted products in 12C(46.7MeV/u)induced heavy ion reactions,both ΔE-E method and fast-slow correlation method are adopted in the particle identification.The response of BaF2 to various incident ions has been studied.
In this paper,some generators of SLq(2/1),satisfying the Serre-like relations,can be considered as 1/2 rank tensor-like operators.The reduced matrix elements of them can be calculated by a set of recurrent formula.Thus th irreducible representations of SLq(2/1) may be completely determined.
On the basis of the old BUU method,the neutrons and protons of the projectile and target nucleus was distinguished,meanwhile,the droplet model which included the surface diffusion parameter,neutron skin and deformation parameter etc.was considered during simulating original nucleon's distribution.Condersing the fact σnp≈3σnn≈3σpp in intermediate energy domain,it was incorapated into the collision term of BUU.Before studying 44MeV/A 86Kr+197Au reaction by the improved BUU model,the stability of the model has been checked,then the condition of nucleons emission was defined,finally the impact parameter dependence of the abraded neutrons and protons from the projectile was obtained,so was the correlation of TLF and PLF.
Under equal time limit,it is shown that the dynamic equations of the n-body correlation Green's functions G(n)c leads to the set of equations for time evolution of the n-body correlations cn and the many-body correlation Green's functions and their equations of motion are independent of the time order.
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