1995 Vol. 19, No. S3
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Two-particle correlations at small relative momenta have been measured for 40Ar induced reactions on 97Au at E/A=25 MeV. The relative populations of states of 4He and 8Be were extracted from p-t and α-α correlation functions, respectively. The temperature of T=3.5±0.81.3 MeV was obtained from relative populations of 8Be states by correcting sequential decay carefully, and the temperature of T=3.6±0.4 MeV was deduced by modifying the sequential decay yield with 30% on 4Heg.s. ground state.
A new heavy neutron-rich isotope 239Pa has been produced in the interaction of 50-MeV/u 18O ions with natU targets. Protactinium products were separated radiochemically from the complex mixture of the reaction products. The results observed from the decay of 239Pa and its daughter, 239U,show that the new heavy-rich isotope 239Pa was synthesized and identified for the first time. The half-life of the 239Pa was determined to be 106±30 min.
Production cross sections of target residues have been measured from the interaction of iron with 135-MeV/u 12C ions, using nuclear chemistry techniques. Mass yield distribution was deduced from the measured cross sections on the basis of a Gaussian charge distribution function. We found that yields at A <30 mass region in this reaction were much higher than those in the reaction of 46 MeV/u 12C+Cu, and those products were partial to neutron-excess. The experimental results were compared with calculations based on the statistical fusion fragmentation model and the modified sequential binary decay model, respectively. It seems to indicate that multifragmentation is one of the dominated reaction mechanisms responsible for production of the fragments with mass number of A <30 at this incident energy.
With Mountain Emulsion Chamber (MEC) data obtained from Mt. Kanbala, the relation between family flux and the energy spectrum of showers in the family is investigated. A Monte-Carlo generator can reproduce the main features of families. It indicated that no global change appeared in the hadronic interaction at the fragmentation region in the energy region from 1014 to 1015 eV.
By using an 28 MeV/u 18O beam, an on-line molten lead target equipment, and 4πΔEβ-γ coincident technique, the relative cross-section ratios and approximate absolute cross section for the neutron-rich nuclides 205-208Hg have been measured; the probable existence of 209Hg is observed and its production cross section is extrapolated. The cross section of 207Hg produced by -2p+1n reaction from the target nucleus depresses suddenly, which may be explained by the variation of reaction Q value.
The identification of τ one-prong hadronic decay using a neural network is presented. Based on the identification, the branching ratios were measured as follows:Br(π/Kv)=(12.18±0.26±0.42)%,Br(π/Kπ0v)=(25.20±0.35±0.50)%,Br(π/K2π0v)=(8.88±0.37±0.38)%, Br(π/K3π0v)=(1.70±0.24±0.39)%.
The removability of the topological term in the 2+1 dimensional CP1 model is studied. Both the classical canonical transformation and quantum unitary transformation for the topological term are obtained. It is pointed out that, in order to give an answer to the question whether the topological term exists or not, one has to study not only the corresponding microscopic spin model but also the vacuum structure of the CP1 model.
Using the method of an eigenvalue equation truncated according to the continuum limit, we calculate the vacuum state of 2+1-dimensional SU(3) lattice gauge theory. The results are consistent with those computed through strong-coupling series in the strong coupling region, and display satisfactory scaling behavior in the weak coupling region.
Using the statistical quark model and the experimental data of hadron yields, we investigate the production rate of quark pairs, the strangeness suppression factor and the ratio of baryon to meson in p collisions. The changes of these quantities with the energy √ are obtained.
The interacting parton model is improved by including the interactions between all kinds of partons in the colliding hadrons and the evolution of parton momentum distribution functions with energy scale. The behaviors of inelasticity and cluster number at high energy are derived without distinguishing soft and hard contributions and without using explicit shape of the parton distribution function.
The two-loop effective potential of the non-topological soliton bag model at finite-temperature and -density is calculated. The influence of thermal effects on the vacuum structure is investigated.
An SO(17) unified model defined in ten dimensions is presented. The model is dimensionally reduced over the coset space SU(3)/U(l)×U/(1)×Z2, giving in four dimensions the standard model with three generations of light fermions.
Based on the three-body model with Yukawa interactions, halo nuclei 11Li, 14Be and 17B are further studied by the variational calculation. An analytical expression for the density distribution of the halo neutron is given. The theoretical results agree well with recent experimental data.
The shape of the emittance contour of a charged particle beam can be described by the contour function. In this paper the variance of the beam contour in nonlinear transport system is studied by means of the contour function theory and Lie algebra. Its inverse problem, the selection of parameters of the transport system according to the beam properties, can be studied also. As examples, the improvement of the beam quality by means of the nonlinear element and the beam matching in the nonlinear periodic field system are discussed.
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