1991 Vol. 15, No. 11
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The measurements of one-dimensional angular correlation of positron annihilation radiation (1D-ACAR) spectra,superconducting critical temperature,lattice parameters and oxygen contents have been made on YBa2－xSrxCu3Oy high temperature supercnductor system.It was found that the substitution of Sr for Ba weakens the orthorhombic symmery,suppresses TC,hardly changes oxygen content and does not disturb the electronic structure of Cu-O chains.Based on the above results.the authors propose that the localized electronic structure of Cu-O plane is a dominating factor for high temperature superconductivity in 1:2:3 phase superconductors.
A search for the neutrinoless double beta decay of 48Ca is carried out in a coal mine which is located 512m underground near Beijing.Large scintillation crystals of natural CaF2 were used as both the detector and the double beta decay source.Result obtained after a total of 7588.5 hours of data taking gives 1.1×1022 years (68%C.L.) as the lower limit of the half-life of the neutrinoless double beta decay of 68Ca.
We have derived the gluon and quark complete propagators under chain approximation in the presence of gluon condensation <Ω│G2│Ω> and quark condensation <Ω│ψψ│Ω>.The nonvanishing vacuum average value for gluon composite operator <Ω│Aαμ(x)Abv(y)│Ω> is expanded into a series in terms of two point distance (x—y) in Lorentz gauge condition.The series is of translation invariance as compared with the series in fixed gauge condition.<Ω│G2│Ω> is introduced as the series coefficient when we take into account the correction of <Ω│Aαμ(x)Abv(y)│Ω> to quark propagator.
Based on the electroweak unified standard model,the probability Pi for the production of i-quark jet (i=u,d,c and b)in e+e－ annihilation has been studied.The probability Pi is a function of energy s.The calculated component ratios of Pu:Pd:Ps:Pc:Pb are 4:1:1:4:1 for s<30GeV.7:9:9:7:9 for s=mz=91.16GeV and 1:1:1:1:1 for s=78 and 117GeV,respectively.Using Pc and Pb,we whave calculated the yields of charmed and beautiful mesons in e+e－ annihilation at s=10—178GeV.
We derive the theory about gauged non-topological soliton stars and their black holes,and find that the gauged Q-stars with maximum particle number Qmax in a definite range of mass are cold, stable and in coherent states of very large mass.Their characteristics are similar to those of general soliton stars.When Q>Qmax,the gauged Q-stars are not stable.
Using the relativized Cornell potential model and with some relativistic correction,we calculate the decay constants of pseudoscalar mesons and the B parameters of D0-D0 and B0-B0 systems.
Based on the basic idea and numerical formulas of EFV different states of nuclei F18,N20,NeF22 and SiF28 in 1s0d shell are calculated.The feasibility of RFV is verified and the importance of various correlations in the procedure is showed.
We solved the problem for both the normal and abnormal finite nuclei from a simple relativistic model,and found eritical mass numbers A1=85 and A2=165.Only nuclei with mass numbers A≥A1 may bave bound abnormal states,and only abnormal nuclei with mass number A≥A2 have binding energies larger than those of corresponding normal nuclei.Abnormal nuclei become unbound again if A>3310,because of the Coulomb repulsion.
On the assumption that ,under the constraints of energy conservation and transverse-momentum cutoff,the rapidities of produced particles by the fireball are distributed with equal probability,multiplicity distributions for different rapidity windows are calculated by using the multisource model.The calculated results fit the experimental data well.
Phenomenological analysis of superdeformed bands in even-even nuclei is given.A method has been developed to determine the spins in superdeformed bands based on the relative energy spacings.
The interaction potentials between two heavy ions are calculated by using the energy density formalism and the nuclear Fermi density distributions,the factor of the neutron skin and the surface diffusion of the neutron distribution increasing with the increases of the neutron excess is considered.In this calculation,the experimental fusion barriers are well reproduced,and improved for the intermediate heavier nuclear systems.It is found that the neutron skin and the neutron distribution diffusion can explain the influence of the neutron excess degree of freedom on the proximity scaling.
The experimental data of the neutron total cross section σt,nonelastic cross section σnon and elastic scattering angular distribution σel(θ) for ten target nuclei ranging from 12C to 238U with incident energies En=20—1000MeV were used to optimize the relativistic phenomenological optical potential (RPOP) through automatic search of the best parameters by computer.In addition,a relativistic microscopic optical potential (RMOP) based on Walecka model were also used to analyze the same data and compare with the RPOP.
Through comparison between these two kinds of relativistic optical potential hints in improving both the RMOP and RPOP is indicated.
In this paper the static characteristic of the nuclear matter characterized by the interior pressure and the binding energy as a function of density is studied with different interactions.By taking into account both the momentum dependence potential and the nuclear medium effect,the dependence of the nuclear collective flow on the impact parameters and the bombarding energies is investigated systematically with BUU dynamical calculations.The nuclear equation of state is better understood by comparing the calculation results with the experiments.
Based on an expanding pure hot quark-gluon plasma fireball which is created by ultrarelativistic heavy-ion collisions,considering the internal occupation number of particle,using relativistic hydrodynamic equation,we investigated the rate of s-quark and K－ -meson production.It is shown that the particle distributions enhance the rate strongly.
We used Monte Carlo method to generate the configurations of disassembly of hot nucleus Au* based on the Atomic Mass Table and the conservation of mass and charge number.The resulted charge distribution of fragments was then used to calculate the conditional moments.The logarithm correlation between second and third moments of experimental charge distribution is very well reproduced by theory.It seems that no connection to the critical phenomenon of concerned system exists.
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