2002 Vol. 26, No. 05

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Letter
Shape Co-existence in 157Yb
ZHOU Xiao-Hong, ZHENG Yong, ZHANG Yu-Hu, GUO Ying-Xiang, LEI Xiang-Guo, LIU Zhong, HE Jian-Jun, LIU Min-Liang, LUO Wan-Ju, WEN Shu-Xian, ZHU Li-Hua, YANG Chun-Xiang
2002, 26(05): 441-444.
Abstract:
The excited states of 157Yb have been studied in the 144Sm(16O,3n) reaction at 16O energy of 90MeV using techniques of in beam γ-ray spectroscopy. The level scheme for 157Yb was established based on the measured results of γ-γ coincidences,γ-ray anisotropies and DCO ratios. The level scheme is dominated by two parallel de-exciting sequences with different characteristics,which correspond to collective rotation and single particle excitations,respectively. This shape co-existence,as well as the structural evolution of the yrast νi13/2band with increasing angular momentum,have been discussed briefly.
Signature Inversion Phenomena in the Rotational Bands of Odd-Odd 176Ir
ZHANG Yu-Hu, WEN Shu-Xian, ZHU Li-Hua
2002, 26(05): 445-449.
Abstract:
High spin states in 176Ir have been investigated via the 149Sm(31P,4nγ)176Ir reaction through excitation functions, X-γ and γ-γ coincidence measurements. Four rotational bands have been identified for the first time and their configurations are suggested on the basis of the existing knowledge of band structures in odd-odd nuclei as well as the measured in-band B(M1)/B(E2) ratios. Among the four bands observed,the πh9/2;νi13/2 and πi13/2;νi13/2 bands exhibit an anomalous signature splitting. The signature inversion point is observed in the former at Ic=18 which is consistent with expectations;this signature inversion spin in the πi13/2;νi13/2 band may be larger than 25h.
Preliminary Study on Ordering Problem in Potential Model
DING Yi-Bing, GUO Peng, LI Xue-Qian, SHEN Peng-Nian, WEI Bing
2002, 26(05): 450-454.
Abstract:
While deriving the effective potential by calculating the elastic scattering amplitude between quark antiquark,one would encounter the ordering problem. Even the hermiticity requirement is considered,various ordering schemes may still lead to different numerical results. We investigate this issue and present the preliminary results,then make some discussions.
Beam Test of a 10 Gaps of MRC Prototype as the TOF Detectors
LI Cheng, CHEN Hong-Fang, SHAO Ming, WANG Xiao-Lian, XU Zi-Zong, ZENG Hui, RUAN Li-Juan, HUANG Sheng-Li, SUN Yong-Jie, WU Jian, YE Shu-Wei
2002, 26(05): 455-461.
Abstract:
A double superlayer of MRPC with 2×5-gas gaps has been tested at CERN-PS (T10) beam line. The prototype has the sensitive area of 200mm×63mm with 2×6 readout pads, which are connected geometrically in series and electrically in parallel. The 45ps time resolution at more than 99% efficiency can be obtained for the 7GeV/c negative pions after the T-A correction.
Particle and field theory
Analysis of Φ Decay to 3γ Final States with the TELESIS
XU Guo-Fa, TONG Guo-Liang, HUANG Xiu-Ping, LV Feng, YU Guo-Wei
2002, 26(05): 462-470.
Abstract:
DAΦNE (Double Annular Φ factory for Nice Experiment) is the Frascati(Italy) electron positron collider operating at the energy of 510 MeV, a rather low energy with respect to the other existing factories. DAΦNE includes two collision points, and KLOE detector is located at one of these points. The KLOE detector is designed primarily for the goal of detecting direct CP violation in K0 decays with a sensitivity of ~10-4 in R (ε′/ε), with a vast amount of other physics subjects. φ radiative dacays, especially its pure neutral final states are very important subjects to test the Chiral Perturbation Theory approach both in the anomalous and non-anomalous sectors. In this paper, a new kinematic fit method—TELESIS—is used for the data analysis of φ radiative decay φ→γη→3γ and φ→γπ0→3γ based on a part of 2000' data collected by KLOE detectors in DAΦNE, the φ produced cross section and the partial cross section of e+e→φ→γπ0→3γ have been obtained as follows:σe+e-→φ=(4.04±0.04±0.24)μb,σe+e-→φ→γπ0→3γ=(5.3±0.3±0.6)nb. These results are in good agreement with that of VEPP and theoretical predictions.
Mass Dependence of Hadron Production Rates in e+e Annihilations at High Energy
WANG Hai-Long, LIU Xi-Ming, WANG Yu-Shui
2002, 26(05): 471-476.
Abstract:
In this paper, the parameter b in the universal mass relation =a exp(-bm) is obtained in virtue of a quark model successfully applied in the field of mass spectroscopy and is found to be a universal parameter for both baryons and mesons. Using this mass relation we give the expression for calculating the multiplicities of all the particles, and calculate the yields of various final state particles and compare it with the data from e+e annihilation experiments and other models. The result shows this universal mass relation can explain experiment as well without any additional assumption.
On the Dynamical Fluctuations in the Production and Evolusion of Jets in High Energy Hadron-Hadron Collisions
YIN Jian-Wu, LIU Feng
2002, 26(05): 477-483.
Abstract:
The dynamical fluctuations in 3 different samples of 630 GeV/c proton-antiproton collisions are studied using Monte Carlo method. These are the mini-bias event sample, the jetty event sample and the sample consisting of the hadrons inside jets. The jets are identified using cone-algorithm. The results show that the jetty event sample mimic the whole event sample in high energy e+e collisions has isotropic dynamical fluctuations, while the dynamical fluctuations inside jets are similar to those of the soft hadronic collisions, being isotropic in the transverse plane but anisotropic in the longitudinal-transverse planes. This shows that the production and evolusion of jets (minijets) have similar dynamical fluctuation property as the production and evolusion of jets in e+e collisions, respectively.
The mini-bias event sample is a mixture of the jet-production processes of hard (semi hard) parton collisions and the soft hadron hadron collision processes. Therfore, it does not have simple dynamical fluctuation property.
Quantization of the Periodic Orbits and Long-Range Correlations in Quantum Spectra
LI Xi-Guo, SONG Jian-Jun, XING Yong-Zhong, ZUO Wei
2002, 26(05): 484-490.
Abstract:
Using the classical quantization way in a two-dimensional integrable system and quantized energies-periodic orbits correspondence relationship, the long-range correlation among the quantum lavels has been discussed in detail. Making use of Berry Tabor trace formula, the quantization conditions of the action of the periodic orbits in two dimensional integrable systems have been obtained. Furthermore, considering the periodicity conditions for the periodic orbits on reasonable torus, the correspondence relations between quantum levels and classical periodic orbits in the two dimensional uncoupled oscillators have been established. It is also shown that there exist the long-range correlations among these quantum levels which correspond to the group of the classical periodic orbits with same topology M(M1,M2). To concert state the new points, an example has been given.
Nuclear and ion Physics
Study on the High-Spin States and Signature Inversion of Odd-Odd Nucleus 170 Ta
DENG Fu-Guo, YANG Chun-Xiang, SUN Hui-Bin, WU Xiao-Guang, LU Jing-Bin, ZHAO Guang-Yi, HAN Guang-Bing, PENG Zhao-Hua, YIN Li-Chang, WEN Shu-Xian, LI Guang-Sheng, YUAN Guan-Ju
2002, 26(05): 491-500.
Abstract:
The high spin states of odd odd nucleus 170Ta were populated via the 155Gd(19F,4n)170Ta reaction with beam energy of 97 MeV provided by the HI-13 tandem accelerator of China Institute of Atomic Energy. Three rotational bands have been pushed to higher spin states and the signature inversion point of the semidecoupled band based on the πh9/21/2⊙νi13/2 configuration has been observed to be 19.5h. The systematic features of the signature inversion in semidecoupled bands in odd-odd rare earth nuclei were summarized. The systematic differences of signature inversion, especially the difference in the energy splitting between the yrast bands and the semidecoupled bands in odd-odd rare earth nuclei are pointed out and discussed for the first time. It seems that p-n interaction between the odd proton and odd neutron in the odd-odd nuclei plays an important role.
Analysis of Multi-Particle Production in 158 A GeV Pb+Pb Collisions by Two-Source Statistical Model
LU Zhong-Dao, SA Ben-Hao, Amand Faessler
2002, 26(05): 501-506.
Abstract:
The data of multi-particle production in 158 A GeV Pb+Pb collisions are analyzed by two-source statistical model. The model calculations fit the experimental data very well and supply a reasonable and clear physical picture. The reaction system is composed of a hot, small inner source and a big, cool outer source. The outer source characterizes the projectile-like and target-like, and the inner source characterizes the central reaction zone. At freeze-out, the system is still in expanding.
Synthetical Analysis of the Spin Assignment for the Superdeformed Bands in A≈190 Region
DI Yao-Min
2002, 26(05): 507-515.
Abstract:
The spin assignment for the superdeformed bands of even-even nuclei in A≈190 region is given by means of using the method of synthetical analysis. In this work, the I(I+1) expression is used to fit the experimental data of the transition γ energies. In contrast to other procedure, the convergence process of the series expansions is put stress upon, whereas taking how many terms exactly in the expression does not emphasized. Moreover as well as the method of fitting the physical quantity, by use of these series expansions the moment of inertia of band heads is also calculated and then the systematics is used for the spin assignments. In practice, when the experimental data is abundant the systematics of the moment of inertia of band heads is more efficient than the method of fitting the physical quantity in the spin assignment. As for a few bands which spin assignment is difficult, the deviation from the typical rotational bands must be considered, which may be judged easily from the second class of moment of inertia of the bands. Finally the results of the spin assignment and the comparison with other literature are presented. These results should be more reliable.
A New Phase of Nuclear Matter under the Condition of High Temperature in QHD Model
JIN Meng, CHEN Ji-Sheng, LI Jia-Rong
2002, 26(05): 516-521.
Abstract:
Form the Lagrangian of QHD Ⅱ, the thermdynamic potential is given in the formalism of finite temperatrue field theory through introducing the effective nucleon mass and effective chemical potential. We analyse the equations of state and find there is a new phase transition in the region of high temperature for the nuclear matter. At last, we give the phase transition diagram.
Critical Behavior of Plasmon Damping Rate in Thermal Scalar Field
ZHANG Han-Zhong, WANG En-Ke
2002, 26(05): 522-529.
Abstract:
Thermal Renormalization Group equations are derived in the framework of Closed-Time-Path formalism in real-time temperature field theory. The numerical solutions of the Thermal Renormalization Group equations show that the coupling constant runs with temperature. Applying Thermal Renormalization Group equations to φ4 theory with spontaneously breaking symmetry, we investigate the critical behavior of the damping rate of the plasmon with finite momentum at the phase transition temperature of restoring symmetry. As the critical point is approached, it turns out that for the plasmon with finite momentum the damping rate decrease to zero. The tendence is opposite to that obtained by taking the no-runing coupling constant. The result is consistent with critical slowing down law.
Accelerator
Developing a Special RF Connector for Coaxial Impedance Measurement Platform
HUANG Gang, HUANG Wen-Hui, CHEN Huai-Bi, ZHENG Shu-Xin, TONG De-Chun, LIN Yu-Zheng, ZHAO Zhen-Tang
2002, 26(05): 530-536.
Abstract:
This paper introduces the development of a special RF connector used in the Coaxial Impedance Measurement Platform. The connector has good broadband transmission performance while the structure of tightening the inner conductor included. The design is done with 3D simulation code MAFIA, the calculated refelection factor less then 0.1 below 20GHz. The measured refelection factor of the manufactured connector is less then 0.2 below 17GHz.
Study on the Electron Optics Property of High-Power Electron Accelerator
YIN Xue-Jun, LIU Zhen-Hao, CHEN Si-Fu
2002, 26(05): 537-542.
Abstract:
This paper studied the electron optics property of a high power electron accelerator using the improved program based on SC program. Some optimieed results were given.
The high-power electron accelerator has many applications in industry. For example, purification of flue gases of thermal power station from Sulphurous oxide and Nitrogen oxide; control and improvement of polyethylene insulation of cables and wires; cleaning of waste water; bactericidal process of grain; presulphuration of tires and study of composite material for soft roofing, etc.