1996 Vol. 20, No. 11
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By an amplitudes analysis of the KKπ system in the J/ψ radiative decay to the K+K－πO and the K0SK±π+ final states, we find that there is one 0－+ resonance (M=1467±3MeV,Γ=89±6MeV) and two 1++ resonances (M=1435±3MeV,Γ=59±5MeV and M=1497±2MeV,Γ=44±7MeV), Which are consistent with the η(1440), the f1(1420), and the f1(1510).
The adaptability of charged hadron multiplicity distributions fitted with negative binomial and its related parameters,forward-backward multiplicity correlation,parameters of clan model,semi-inclusive rapidity distribution and the seagull plots describing the characteristics of transverse momenta of jets are discussed. In particular,the above mentioned parameters in restricted rapidity intervals are analysed and comparde with theoretical results of some phenomenological models of multiparticle production. Most of the results are obtained from 50000 Z0 events of ALEPH Collaboration at LEP.
According to the Minimal Standard Model and the Extended Standard Model with two Higgs doublets, we calculated the total cross sections and differential cross sections for the e+e—→bb Z0 and tt－Z0 at the LEP Ⅱ and NLC energies in order tO study the possible observational effects of the Higgs particle. We found that the observation for the e+e—→bb Z0 can give the information on the Higgs particle as long as the mass of the Higgs particle MH≤140GeV. However, for the e+e—→tt－Z0 the effect from Higgs particle will be completely suppressed by the electrowead background and cannot be observed, no matter whether the Higgs particle is heavy or light.
The strangeness production in high energy pp collisions is studied by considering the constraint from the isospin conservation and the suppression of strange quark production. The multiplicity dependence of the ratios K+/π+and K－/π－ is given, and an approximately parameter independent ratio of (K+/π+)/(K－/π－) is proposed to reflect the constraint of isospin conservation.
In a realistic effective one-family extended technicolor(ETC)model without exact custodial symmetry, we calculate the one-loop corrections to the Zbb and Zτ+τ－ vertices from the sideways and diagonal ETC gauge boson exchange.The results show that both the Z→ bb partial Width Γb and branching ratio Rb and the τ polarization asymmetry parameter Aτ are enhanced by the corrections and are in agreement with the present experimental data.
The influence of the initial state intcractions on the J/ψ production-rate supression in p-A collisions is studied. The incident proton energies decrease due to the inelastic interactions with the target nucleus. Considering energy loss of the incident proton,the data are well reproduced by using the final state interaction cross section σfabs=2.1mb.
A two-body correlation transport theory(TBCTT) for describing the dynamical process in heavy ion collisions(HIC)is established by means of time-dependent coherent single particle state representations and the two-body correlation dynamics.Containing time-dependent mean field effect, Pauli block, and two-body collisions,this model is capable of describing the time-evolution of nonuniform nuclear matter,fluctuation effects and dynamical formation of fragments in HIC.
The Fermi-Dirac correlation of identical protons is studied. Based on the non-perturbative theory of quantum fields, we put farward a kind of source distribution-the Q－v)Kv(Q) distribution. The Fermi-Dirac correlation of(p±-p±）-pairs is calculated from this distribution. The fitted curves agree with experimental data. The Q－v)Kv distribution has more advantages than the Gauss Source distribution. The radii of the source emitting hadrons and the anomalous dimensions of the Fermi field are calculated from the Fend-Dirac correlation of identical protons.
Under the distorted wave impulse approximation, we discuss the antiprotonnucleus charge exchange reaction A(p,n)B and the inelastic scattering ACalculations are presented for the differential cross sections of 12C(p,n)12B,18O(p,n) 18N and 18O(p,n)18O at antiprotion energies 179.7MeV and 46.8MeV. Distorted wave functions are calculated by the exact partial wave method. It is shown that the theoretical inelastic scattering results fit the experimental data quite well. The theoretical resultes of the diferential cross sections for antiproton-nucleus charge exchange reactions are also predicted.
The existence of the △I=4 bifurcation is confirmed via an overall investigation of the A～190 superdeformed bands. The behavior of the bifurcation amplitude is also discussed.
The bunch length and its lengthening in the BEPC were measured systematically and carefully with streak camera and the method of beam spectrum analysis in recent years. The results are obtained from the measurements and the corresponding scaling law is summed in the light of the existing theoretical explanation.
This paper reported a new shape of practicing single-cell superconducting cavities. It consist of the two half end-cell of 9-cell Beijing TESLA shape accelerating cavity. The ratio of the maximal surface electric field to accelerating gradient,Ep/Eacc,of the π-mode of the 9-cell cavity is reduced to 2.024. The cell -to-cell coupling k is high to 1.95%. The Ep/Eacc in the single-cell cavities is reduced to 1.8.The monopole, dipole and quadrupole high-ordermodes, HOM, was calculated with resistance-band model using URMEL-T. In addition, the concept of the structure parameters of niobium cavity was introduced as well as the condition of calculation reliability with codes, URMEL and URMEL-T, was discussed.
An exact expression for calculating the in-medium △ absorption cross section is obtained within the framework of the self-consistent relativistic BUU approach. The medium effects on the △N→NN cross section is investigated, and it is found that the effective cross sation is suppressed in the medium near the threshold energy. The results are in a good agreement with the most recent experimental data of the TAPS collaboration.
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