1994 Vol. 18, No. S2

Display Method:          |     

Subbarrier Complete Fusion-Fission Reactions of 16O+232Th
Liu Zhuhua, Xu Jincheng, Zhang Huanqiao, Qian Xing, Qiao Yu, Lin Chengjian, Xu Kan
1994, 18(S2): 121-128.
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.
Absolute Efficiency of A φ76mm×100mm BGO Scintillation Detector
Liu Xin, Ye Yanlin, Jiang Dongxing, Lu Xiting, Liu Hongtao
1994, 18(S2): 129-134.
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.
A Semi-experimental Method to Determine the Efficiency of ττ→eμ(υ) Event Selection
Chen Hongfang, Lü Feng, Tong Guoliang, Wu Jian, Wu Yigen, Xu Mianhai, Xu Mingkang, Xu Yadi, Ye Shuwei, Yu Yanhua, Zeng Jiyang, Zhong Chongchang, Zhu Hongguo
1994, 18(S2): 135-140.
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.
Angular Distribution of Processes e+e-τ+τ-,τ-→a1-υτ,a1-ρπ and Characteristics of a1 Meson
Yu Hong, Shen Qixing, Zhang Lin
1994, 18(S2): 141-150.
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.
Model Dependence of the BSW Approach
Luo Chuanwang, Huang Tao, Guo Xingheng, Li Jinping, Lu Goungru
1994, 18(S2): 151-166.
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.
Transverse Motion Correlation of Collective Flow in Relativistic Heavy Ion Collisions
Liu Yiming, Zhang Weigang, Huo Lei, Wang Shan, D. Keane, S. Y. Chu, S. Y. Fung
1994, 18(S2): 167-174.
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.
On the Intermittency and Correlation Integral of Multiparticle Final-States in High Energy Collisions
Zhang Yang, Hu Yuan, Wu Yuanfang, Liu Lianshou, Zhang Yonghe
1994, 18(S2): 175-184.
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.
Absorption Correlation in Pion Interferometry Analyses
Huo Lei, Zhang Weining, Wang Shan, Liu Yiming, D. Keane, S. Y. Chu, S. Y. Fung
1994, 18(S2): 185-192.
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.
Anti-proton-Nucleus Inelastic Scatterings at Intermediate Energies
Li Yangguo
1994, 18(S2): 193-200.
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.
Color Screening Effect in bb System
Dong Yubing, Shen Pengnian, Yu Youwen, Zhang Zongye
1994, 18(S2): 201-206.
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.
Inclusive (π,η)Reactions on Nuclei
Chen Lin, Jiang Huanqing
1994, 18(S2): 207-213.
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.