2000 Vol. 24, No. 7
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Using the data collected with Beijing Spectrometer (BES),we have measured the total cross section for e+e－ annihilation into hadronic final states around center-of-mass energy 3.55 GeV. The values of R,σ (e+e－→hadrons)/σ(e+e－→μ+μ－),are determined with smaller error than the previous result by a factor of two.
In this paper,a model-independant amplitude for the decay process of ψ′→J/ψ π+π－ is constructed from a few basic rules:Lorentz invariance,PCAC (Partial Conservation of Axial Current) and QCD low energy theorem. Based on this amplitude, a new and complete partial wave analysis to this process is carried out. Formulae of angular correlation distribution,invarant mass spectrum and two dimension (joint angular correlation and invarant mass) distribution are given. It is pointed out that there exist D-wave in the ψ′→J/ψ π+π－process and part of the D-wave is caused by recoil of J/ψ.
The tensor charges of the nucleon are calculated by using the QCD Sum Rules in the external tensor field,where the nucleon interpolating field(nucleon current operator)takes the most general form,i.e.the unconventional one . Calculation includes the terms up to demension 8. All possible effects on QCD sum rule calculations of tensor charges of the nucleon by changing interpolating field and tensor susceptibilities are analysed. The calculations show that the stable solution for QCD sum rules of tensor charges of the nucleon can not be obtained by changing interpolating field and tensor susceptibilities. However,the stable behavior of the solutions for the sum rules of isovector and isoscalar tensor charges may be improved when the interpolation field takes the best one. The tensor charges of the nucleon by taking average over the so-called“sum rule window”are given.
It is important to give a set of wave functions of arbitrary spin particles for the analysis of amplitudes in high energy processes.From Bargner-Wigner equations about high spin states we constitute a set of tensor equations of integral spin particles. By solving the equations,we write the covariant states of arbitrary integral spin particles, including canonical states and helicity states. Finally,we give the effective Lagrangian formalism of the equations.
The coupled cluster method is improved to calculate sixth order coefficients μF0,μF2 and relevant parameter ζ of glueball wave function in 2+1-D SU(2) lattice gauge theory (LGT). In the calculation,we select hollow graphs as trial wave function. The calculated results of μF0,μF2 and ζ show good scaling behaviors at weak coupling region.
The renormalization coefficient matrix and anomalous dimension matrix of two three gluon tensor operator Ωαβ1=Gαa,μ Gμb,ν Gνβc fabc and Ωαβ2=gαβ Gσa,μ Gμb,v Gνc,σ fabc,which are closely related to the glueball current operator with quantum number JPC=1－+, were calculated. The divergent terms of amputated three point Green function of Ωαβi (nonzero momentum transfer) in Lorentz gauge were calculated explicitly up to g2s order,and no other gauge invaraiant operators were found to mix with them. Defining αβ1=Ωαβ 1-14Ωαβ2, the physical part of renormalization coefficient matrix of αβ1 in minimum subtraction scheme with space dimension D=4+2 is Z1=1+g 2s C A(4 π)276+O(g4s). The Physical part of anomalous dimension matrix of αβ1 is gauge invariant, and γ1=g2 sCA(4π)273
The equivalent ρ-and ω-meson exchange spin-orbit potentials of NN interaction are studied from the one-gluon exchange quark-antiquark pair creation model. The results show that both the equivalent ρ and ω-meson exchange spinorbit potentials are similar to those of the conventional meson exchange theory.
A new transport model (isospin dependent Boltzmann-Langevin equation)is developed and it is shown that this model can regenerate the experimental data for reaction of 12C+12C at 28.7MeV/u. The production cross section of 19Na is systematically studied for reactions of 17—20,22Ne+12C at 28.7 MeV/u.It is found that a neutron deficient projectile has larger 19Na cross section than a stable projectile.
Nucleon density distributions in nucleus (including neutron and proton)have been introduced into the Abrasion-Ablation model for the intermediate energy collision.Process of projectile fragmentation in the reaction of 30MeV/u 40Ar+natAg has been simulated with the model of corrected version. The results show that in the rather peripheral collisions there are obvious differences for the calculated cross sections with and without correction of nucleon density distributions in the model.The differences come from the effects of dispersion on the edge of nuclei. It has been verified by comparison with experimental results that reduction of mean energy of projectile-like fragments from beam energy is mainly caused by the action of friction.
The effect of the nonlinear terms on the resolution power and measuring accuracy of the circular mass spectrometer is analyzed. Related expressions for determing these effects are given.
Hefei synchrotron Light Source(HLS) presently has three kickers for injection,and different lattices will form different shapes of bump orbits In order to relieve the dependence between bump and lattice,a compact injection scheme,in which four kickers are located at the same straight section,is proposed.Because the straight section for injection is too short,it needs kicker to produce strong magnetic fields.This paper looks into the possibilities of using orbit correcting trim coils to make assistance DC bump orbit to reduce kickers strength.The different schemes and their advantages are discussed.
A new method of arbitrary variation of the phase of RF system during the macropulse to optimize the FEL output is proposed. In this method, the FEL output is used as a tuning indicator to adjust the RF phase in different time intervals of the macro pulse with computer controlled arbitrary function generator. In this case, shortest build up time and largest saturated power in a macro pulse can be simultaneously achieved. Experimental testing of this method has been carried out in Beijing IR FEL oscillator and proves to be effective in increasing the power output of BFEL facility.
Modifications in optical absorption of polyethylene terephthalate(PET) films induced by 35MeV/u Ar ion irradiation were studied by means of ultraviolet-visible absorption spectroscopy.A strong increase in absorbance in the ultraviolet and visible regions is observed in the irradiated samples, which is attributed to the formation of a conjugated system of carbon bonds.The effect is found to increase with increase of ion fluence and the mean electronic energy loss in the samples,but to decrease with increase in the optical wavelength.According to the measured optical absorption spectra,modifications of optical energy gap and the mean size of carbon clusters of the PET samples under irradiation are also analyzed and discussed.
The spectra of baryons which include two heavy quarks and one light quark can be treated as a two-body system,where two heavy quarks constitute a bosonic diquark.We derive the effective potential between the light quark and the heavy diquark.In this work we have discussed several serious problems:(1)the operator ordering,(2)the errors caused by the non-relativistic expansion,(3)spin-spin coupling and (4)the mixing between baryon states with scalar-diquark and vector-diquark.
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