1995 Vol. 19, No. S2
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The nuclide on proton drip line 19Na was studied through a 20Ne(p,2n)19Na reaction. Its new decay mode of β-delayed proton decay was observed for the first time. The proton energy was measured to be 1.10±0.08 MeV and its half-life was determined to be 47±20 ms, which corresponds to a superallowed β transition of l9Na ground state to 19Ne 7.62 MeV isospin analog state with T=3/2, and subsequent proton emission to an 18F ground state.
Before the τ mass experiment, several measurement strategies were studied in detail by Monte Carlo simulation. After they were widely compared, the likelihood method was suggested to determine the energy points, and the possible measurement accuracy has been given. The effects of many factors of the measurement were simulated, such as the event selection efficiency and energy spread, and necessary req requirements were proposed for the experiment.
Based on 7.8×106 J/ψ events collected by the BES at BEPC, the hadronic decays J/ψ→ϕπ+π- and J/ψ→ωπ+π- are studied, and the branching ratios of these process and the mass and width of f0 are obtained. The angular distribution of J/ψ→ϕf0, f0→7π+π- is fitted and the helicity amplitude ratios of this process are given for the first time.
The pseudorapidity distributions of charged particles produced in pp collisions at 400 GeV/c have been measured by using the LEBC films offered by the CERN NA27 Collaboration. The scaled factorial cumulant moments have been calculated. Compared with the results obtained from Monte Carlo events with the same single-particle spectrum and no correlations, a significant part of K2 for broad mixed multiplicity distributions comes from single-particle density fluctuation owing to the fluctuating multiplicity. The factorial cumulant moments obtained by using the star correlation integrals reduce significantly the statistical errors of the higher order cumulant moments, but the essential conclusions remain unchanged.
From the chiral Potts model the "inversion" and "star-square" relations of the Baxter-Bazhanov model are obtained. The tetrahedron equation, which is a commutativity condition for the three-dimensional cubic lattice, is a consequence of the star-triangle relation of the chiral Potts model. The additional constraints in tetrahedron equation hold naturally when the Boltzmann weights are parameterized in terms of the Zamolodchikov angle variables. It is pointed out that the star-triangle relation of the three-dimensional model, which includes the result of Baxter-Bazhanov's, can be obtained by using the method given in this paper.
In the Lattice gauge theory, by using the variational cumulant expansion, we calculate the internal energy and specific heat for the two-dimensional 0(3) nonlinear σ model. A comparison with the Monte Carlo (MC) result is also presented.
In this paper the generalized Noether's identities for nonlocal transformations are derived from the properties of the action of a system under local and nonlocal transformations. In the application of the theory to the Yang-Mills field with high-order derivatives, a new conservative PBRS charge, which differs from the BRS conservative charge, and a new conservative charge connecting with nonlocal transformations are found.
Based on the interacting gluon model (IGM), leading particle rapidity distributions for 100 GeV p+Ag collisions are calculated and compared with experimental data. The results are in agreement with data obtained from using a more sophisticated collision geometry and including final-state fragmentation process.
The contributions of the double pomeron exchange (DPE) to the production of high-energy p+ p( ) collisions are calculated using both the Ingelman-Schlein model and the Donnachie-Landshoff model of the parton distribution functions for the pomeron (P). For the D-L model, in which gluons dominate the pomeron, the cross sections at high energy increase with energy √ as ln2S or InS. Its total cross section, σ(S), is about 102-103 nb in the TeV energies region. For the D-L model, in which P is considered a nonperturbative gluons system and its coupling with quarks is something like isoscaler photons with C=+1, its cross-section behavior with energy is a bit complicated. In the same energy range as in the D-L model, cross sections in the D-L model are only 1-3 nb, which is smaller than that of the former by 2-3 orders of magnitude. So if we assume that the parameterizations of both models are reliable, their J/ψ production processes should themselves become a good means of testing these models.
From the full stopping scenario, we have studied the dilepton spectrum on the basis of the (3+1) dimensional RHE, and come to the conclusion that with increasing initial baryon density the dilepton production in invariant masses between 2 mx to 1 GeV is shown to be suppressed, and an abnormal peak of the dilepton spectrum appears near the invariant mass 0.75 GeV if the baryon-rich quark-gluon matter is indeed created in ultrarelativistic nuclear collisions. These predictions will be tested in future experiments at CERN and Brookhaven.
By means of the instantaneous Bethe-Salpeter equation, the effect of negative energy components of the Dirac spinor on the one-gluon exchange interaction is studied. Through the calculation of the N and Δ baryon spectra. One sees that the inclusion of the negative-energy components changes the potential parameters significantly, especially for αs. However the global structure of the spectrum is almost untouched.
The surface energy coefficient of nuclear matter σ(T,δ) is calculated, using the semi-infinite model of nuclear matter, as a function of temperature T and nuclear asymmetry δ by the temperature-dependent Thomas-Fermi statistical model theory, with the Seyler-Blanchard momentum-dependent nonlocal interaction. It is found that the surface energy coefficient can be written approximately as σ(T,δ)=σ0(T)[l+K(T)δ2], where the σ0(T) and K(T) can be fitted as quadratic functions of temperature T.
The identical superdeformed bands of odd-A nuclei in the A ~190 mass region have been investigated by using the triaxial-particle-rotor model within the framework of the BCS pairing correlation. Three pairs of identical bands-(19lAu, 191Hg(bl)), (191Hg(b2), 193Hg(b2)), and (191Hg(b3), 193Hg(b3))-are analyzed. It is pointed out that the identity in the γ-transition energies in these bands may be the result of the occupation of some special orbitals.
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