1994 Vol. 18, No. 6
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Angular distributions and differential range distributions have been measured with nuclear chemistry techniques for 20 target residues from the reactions of 115In with 92 and 71MeV 16O ions.In terms of the increase of impact parameter,the results indicate continuous evolution of the reaction mechanisms from complete fusion,incomplete fusion to direct reaction involving steadily decreasing transfer of mass and momentum.Contribution of incomplete fusion in 16O+115In reaction is significantly larger than that in 16O+65Cu reaction.
We have succeeded in isolating the complete arising from complete fusion-fission in terms of the fragment folding angle technique,and measured complete fusion-fission cross sections and fragment angular distributions for the 16O+232Th system in the center-of-mass energies between 72.61 and 80.11 MeV.The observed fission excitation function is in quite good agreement with the expectation of the coupled-channels theory.However,the measured fragment angular distributions are more anisotropic than the predictions of both the saddle-point transition-state model and scission model.
With several monoenergetic gamma-rays generated at low energy(p,γ)resonant nuclear reactions,the full-energy-peak intrinsic gamma-rays detecting efficiencies of a Φ 76 mm×100mm BGO scintilation detector were measured as below:7%、9%、22% at 17.65、17.23 and 6.13MeV gamma-rays energy,respectiviy.
With a Bhabha events generator the Bhabha scattering effective integral cross section for Beijing Spectrometer(BES)luminosity monitor is calculated based on the parameters of the monitor and Beijing Electron-Positron Collider(BEPC)beams.This cross section value can be used for calculating the luminosity of BEPC beams with the systematic error less than 3%.The measured data are in good agreement with the calculation.
With 4πdata for 1.2A GeV Ar+BaI2 and 2.1A GeV Ne+NaF collisions at the Bevalac streamer chambe,the transverse motion correlations arising from collective flow are studied include azimuthal correlations and correlations of transverse momentum magnitude.The azimuthal correlations of particle distribution,the correlations of transverse momentum magnitude and transverse motion in collisions of Ar+Bal2 are stronger than the corresponding ones in collisions of Ne+NaF respectively.Comparing with the correlations of transverse momentum magnitude, the azimuthal correlations dominate correlations of transverse motion in two experimental samples.
The fundamental Poisson structure of nonlinear O(3)-σmodel,treated as a constrained dynamical system, is discussed in arbitary local coordinate frame.The corrsponding r,s-matrices,which are generally field dependent,are presented explicitly.It is noticed,however, that in a certain local coordinate frame,r,s-matrices will be field-independent.
By means of the imaginary-time Green function method in finite-temperature field theory,one ρ-meson exchange potential at finite temperature is obtained.It is found that ρ-meson become lighter in terms of temperature increasing.The result is in good agreement with that obtained from scalling property of QCD.It is also found that temperature dependence of ρ-meson coupling constants is similar to that of,σ-meson coupling constants.
The Taylor expansions of the quark and mixed condensates are presented Lorents gauge,which as well as the expansion of gluon condensate can be used to calculate the Wilson coefficients of the nonperturbative correction terms in the operator product expansion. In contrast to those current expansions in the sum rules in the fixed gauge,the new expansion has the advantage of being translational invariant.
Extending fermion dynamical symmetry model to includ fermion pairs with higher angular momentum can lead to SO(4i+2)or SP(4k+2)dynamical symmetry group,This paper gives a discussion about their representations of the exact Dyson boson image and of the Pauli principle in Dyson boson image.
The spectra,leptonic decay widths and the E1 transitions of system are calculated,with the confining potential including the color screening effect as a color confinement between quark and antiquark.The relativistic correction to the E1 transitions is also considered.
By assuming that the ηN reaction is dominated by the N(1535)resonance,the A(π,η)X inclusive reaction is studied in the framework of the DWBA model,and double differential cross sections are calculated for the 12C(π,η)X inclusive reaction.A good agreement between our theoretical result and the experimental datais achieved,and it is found that the interaction between N and N is attractive.The Pauli blocking effect is not obvious for the η production process.
The equilibration in relativistic heavy ion collisions ie studied with relativistic BUU theory.It is found that the mean field still play an important role in addition to the collison term of the equilibration process in relativistic heavy ion collisions at energy arround 1GeV/n.The influence of the medium effects is studied.The light and medium systems do not reach complete equilibrium so that the concept based on the complete equilibrium is questionable for this case.
The proposed hadronic transport model for rescatterting of pion is used to investigate the K+/π+ ratio in p+p,p+Au and Si+Au reactions at AGS energy(14.6AGeV/c).Experimental evidence of increasing continuously of the K+/π+ ratio from p+p to p+Au to Si+Au at similar incident energy per nucleon is reproduced reasonablely.The experimental fact of K+/π+ ratio at CERN energy is comparable with corresponding result at ACS energy,is reproduced as well.
Beijing FEL is a rf linac based facility designed to work in the IR spectrum rang. In this paper,system layout is first briefly reviewed.Then various measurements adopted to optimize the electron beam quality for the lasing requirement are described.Spontaneous emission,stored spontaneous emission and lasing were observed in sequence.Optical spectrum,detuning curve and wave length shift were measured to confirm the first lasing.
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