1994 Vol. 18, No. S2
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We have succeeded in isolating the complete fusion-fission from transfer-induced fission in terms of the fragment folding angle distribution technique, and measured the 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 model. However, the measured angular distributions are more anisotropic than the predictions of both the saddle-point model and scission-point model.
Using monoenergetic gamma-ray generated from low energy (p,γ) resonant reactions, the full-energy-peak gamma-ray detecting efficiency of a φ76mm×100mm BGO scintillating detector was measured. The efficiencies of 7%, 9% and 22% are obtained at gamma energies of 17.65, 17.23 and 6.13 MeV, respectively.
The efficiency of event selection is an important parameter in the measurement of the r lepton mass. In our study we used so-called semi-experimental method in which we combine M.C. and experimental data. With this method the efficiency of selecting ττ→eμ(υ) is obtained as (14.5±0.7±0.8)%,and various relevant corrections are discussed. The result is consistent with that derived from two-parameter fitting of the τ lepton mass.
The density matrix and the helicity formalism of the angular distribution of the processes e+e-→τ+τ-,τ-→a1-υτ,a1-→ρπ are obtained. The helicity amplitude ratios corresponding to the form factors of the W-a1 transition and the strong interaction vertex a1ρπ can be determined by the sectionalized fitting method. Then a model-independent method is given for precisely determining the mass and the width of the very broad resonance a1.
Hadronic model wavefunctions are applied to calculate hadronic matrix elements of decays of D,B mesons in the Bauer-Stech-Wirbel (BSW) approach. We have analyzed several different models of valence Fock state wavefunctions, studied their properties and calculated branching ratios of weak decays of D,B mesons. The results show that predictions of the different wavefunction models can fit most of the present data within the errors by choosing reasonable a1 and a2. Therefore, for studying the model dependence and the reliability of the BSW approach it will be helpful to further investigate the factorization of weak processes and the hadronic wavefunctions theoretically and to further perform more accurate experiment measurements.
With 4π data for 1.2 A GeV Ar+BaI2 and 2.1 A GeV Ne+NaF collisions at the Bevalac streamer chamber, the transverse motion correlations arising from collective flow are studied, which include azimuthal correlations of particle distribution 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-f-BaI2 are stronger than the corresponding ones in collisions of Ne+NaF respectively. Comparing with the correlations of transverse momentum magnitude, the azimuthal correlations of particle distribution dominate correlations of transverse motion in two experimental data samples.
It is shown by both theoretical analysis and Monte Carlo simulation that using the correlation integral instead of factorial moments in the investigation of intermittency phenomena will change the anomalous scaling behavior for decreasing rapidity bins. It is pointed out that the correlation integral and factorial moments probably reflect different physical aspects. In order to eliminate the artificial factor in bin-division, a method of randomly moving starting point of bin-division in the investigation of factorial moments is proposed. It is also shown that the spike events have important contribution to the intermittency indices.
The effect of absorption on the analyzed results of pion interferometry is studied. The removal of this effect is investigated using a VUU simulation. Data for collisions of 1.8 A GeV Ar+Pb at the Bevalac streamer chamber are analyzed. The spatial parameter of the source extracted from pion interferometry is less than the true value due to the absorption correlation. The effect of the absorption correlation can be eliminated by properly constructing the background.
The distorted wave of anti-proton is obtained by an optical potential derived from the multiple scattering theory. In the framework of the distorted wave impulse approximation, we discuss the antiproton-nucleus inelastic scattering at intermediate energies. The inelastic differential cross sections of 12C(p,p')12C*,2+,3- states at anti-proton energies from 180 MeV to 1800 MeV are calculated. It is shown that DWIA fitted the experimental data quite well, and theoretical results of inelastic cross sections at higher energies are predicted.
The spectra, leptonic decay widths and El transitions of the bb system are calculated with a confinement potential in which the color screening effect is included. Meanwhile, the effect of relativistic correction on El transition is also evaluated.
By assuming that the η-N interaction is dominated by the N*(1535) resonance, the inclusive (π,η) reaction is studied in the framework of the DWBA model, and the cross sections are calculated for the inclusive 12C(π,η)X reaction. A good agreement between our theoretical result and the experimental data is achieved, and it is found that the interaction between the N* and N is attractive. The Pauli blocking effect is not obvious for the η production process.
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