1995 Vol. 19, No. 07

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Review
Study of ψ(2S) Decay to τ Lepton Pairs
BES Collaboration
1995, 19(07): 577-584.
Abstract:
The decay ψ(2S) →ττ has been studied by using the 1.27 million ψ(2S) events produced from the BES experiment at the BEPC collider. The ττ decay branching ratio is for the first time measured to be (3.54±0.61±0.63)×10-3, which is consistent with the prediction of the hypothesis of e-μ-τ universality. Combiningthis value with the previous leptonic data of ψ(2S), the total width of the ψ(2S) is found to be 251±37keV.
Anomaly Observed in Subbarrier Fusion-Fission Reactions
Liu Zuhua, Zhang Huanqiao, Xu Jincheng, Qian Xing, Qiao Yu, Lin Chengjian, Xu Kan
1995, 19(07): 585-590.
Abstract:
The fusion-fission cross sections and fragment angular distributions for the systems of 16O+232Th, 16O+238U and 19F+232Th at near-and sub-barrier energies have been measured. The enhancement of fusion-fission cross sections at subbarrier energies is well explained in the framework of coupled-channels theory in which the target static deformations are explicitly taken into account. However, the experimental fragment anisotropies obviously deviate from the predictions of the statistic fission model.
Relation Between Temperature and Excitation Energy of Hot Nuclei in the Reaction of 40Ar+197Au at 25MeV/u
Wu Heyu, Jin Genming, Li Zuyu, Dai Guangxi, Qi Yujin, Luo Qingzheng, He Zhiyong, Duan Limin, Zhang Baoguo, Dang Bingrong, Wen Wanxin
1995, 19(07): 591-597.
Abstract:
For the reaction of 25MeV/u 40Ar with 197Au, coincidence measurements have been made for the heavy residue fission fragments and light charged particles (Z≤2). The folding-angle and time of flight of heavy residue fission fragments were used to deduce the linear momentum transfer (LMT). The initial properties of these nuclei, excitation energies, angular momenta and temperatures, have been studied by measurements of LMT and light particle spectra. The relation between the excitation energy per nucleon and temperature is analysed by different windows of LMT. It is shown that the hot nuclei are close to saturation of temperature for central collision and close to "phase transition for multifragmentation".
Tracks of Binary Decay
Wen Wanxin, Dai Guangxi, Wu Heyu, He Zhiyong, Luo Qingzheng, Duan Limin, Cai Wei, Jin Genming, Li Zuyu, Zhang Baoguo, Qi Yujin
1995, 19(07): 598-602.
Abstract:
The tracks of a few successive decay events in the reaction of 19MeV/u 40Ar+209Bi are observed in muscovite sheets as solid track detectors. It is deduced that the time interval between two successive decays of these events is about 10-13s. From calculation based on the WKB approximation for barrier penetration it is believed that such successive fission is possible.
Cross Sections of Evaporation Residues of 12C+93Nb in the Vicinity of the Coulomb Barrier
Qian Xing, Jiang Dongxing, Lin Junsong, Liu Daming, Li Ze
1995, 19(07): 603-611.
Abstract:
Cross sections for 8 products from the fusion reaction 12C+93Nb in the projectile energy range from 28.3 to 45.7 MeV have been obtained by off-line γ technique.The experimental results have been analysed in terms of the simplified coupledchannel model, including the coupling of the inelastic excitation and transfer channels, and statistical model for the compound nuclei. As a result, the excitation functions for the neutron emission channels are well reproduced by the CASCADE code. In the case of proton, alpha emission channels show higher cross sections than the CASCADE predictions. The transfer of alpha particles as doorways to fusion seems to be the main process which is responsible for the fusion enhancement. The experiment shows that the reaction system has large transfer cross section at subbarrier energy.
Production rate of Quark Pairs, strangeness suppression factor and ratio of baryon to meson in pp collisions
chen esheng, chen yan
1995, 19(07): 612-619.
Abstract:
using the statistical quark model and the experimental data of hadron yields,we investigate the production rate of quark pairs, the strangeness suppression factor and the ratio of baryon to meson in pp collisions. the changes of these quantities with the energy s are obtained.
High Energy Behaviors of Inelasticity and Cluster Number in Interacting Parton Model
Wang Qun, Liu Ximing, Xie Qubing
1995, 19(07): 620-627.
Abstract:
The interacting parton model is improved by including the interactions between all kinds of parlous in colliding hadrons and the evolution of parton momentum distribution functions. The high energy behaviors of inelasticity and cluster number are derived without distinguishing. Soft and hard contributions and without using the explicit shapes of parton distribution functions.
Cross Section of In-medium Nucleon-Nucleon Inelastic Scattering (Ⅱ)
Mao Guangjun, Li Zhuxia, Zhuo Yizhong, Yu Ziqiang
1995, 19(07): 628-636.
Abstract:
The screening effects on the cross section of the in-medium nucleon-nucleon inelastic scattering are investigated within a relativistic self-consistent description.
Possible Manifestation of Quark-Gluon Plasma in Multiplicity Distributions in High Energy pp(p) Collisions
Chen Fence
1995, 19(07): 637-645.
Abstract:
Based on the Quantum Chromodynamics Bag and Statiscal Hydrodynamical Model (QCDB-SHM),. the inital fireball produced in high energy pp (p) collisions is discribed under the approxmation of two dimensional equilibrium state. The relation between the multiplicity and center-of-mass energy obtained is in a good agreement with the experimental date of the nondiffractive processes. The side-fire ball of source Ⅱ is discribed under the approximation of three dimensional equilibriumstate. The relation between the transverse momentum and average size of the sidefire ball obtained fits well the date calculated by the Three Fire Ball Model.
Studies of Some Exotic Properties of 6—11Li Nuclei in the Framework of Shell Model
Dai Lianrong, Gu Jinnan
1995, 19(07): 646-652.
Abstract:
The possible microscopic mechanisms of some exotic properties of 6—11Li nuclei,especially for dripline nucleus 11Li are investigated in the framework of Shell Model. The quadrupole moment of the ground state of 6Li is primarily sensitive to the tensor components of interactions. The electromagnetic transition probabilities of the first excited states of 6—8Li nuclei are extremely enhanced. The collectiveness possibly results from cluster structures. In the vicinity of 3≤Z ≤5 and N≈8,there may exist the phenomenon of crossed-shell excitation and/or N=8 shell gap disappeariance.
4π△Eβ Detector and Its Application to Researching Neutron-Rich Nuclides
Wang Jicheng, Zhao Jinhua, Guo Guanghui, Yang Yongfeng, Zhang Li
1995, 19(07): 653-657.
Abstract:
A 4π△Eβ detector has been set up. Its time response is very good and the rising time is 8ns. By using 4π△Eβ-γ coincidence technique, the γ intensity of neutron-deficient nuclides followed by electron capture is strongly suppressed, but the coincidence efficiency about γ line followed by 100% β-decay in neutron-rich Hgnuclides reaches highly 60%. The application of this detector to 18O+208Pb experiment made the Compton background descend sharply.
Design and Study of Beam Dynamics for the BPL-RFQ
Luo Zihua, Wang Shuhong
1995, 19(07): 658-666.
Abstract:
The choices of parameters and design study of beam dynamics for the BPLRFQ are described in this paper. And the basic parameters of the BPL-RFQ system have been also given.
Quark Mass Matrices and CP Violation
Xing Zhizhong
1995, 19(07): 667-671.
Abstract:
We explore the exact analytical relations between a variety of quark mass matrices and CP violation Our results can be applied to the phenomenological studies of different ansatz of mass matrices and their CP-violating effects.