2001 Vol. 25, No. 10

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Particle and field theory
Calculation of the 0++ Glueball Mass for 2+1 Dimensional QCD by Using the Improved Lattice Hamiltonian
JIANG Jun-Qin, LI Jie-Ming
2001, 25(10): 941-944.
Using the improved lattice Hamiltonian and the truncated eigenvalue equation method, we com- pute the 0++ glueball mass for (2+1)-dimensional QCD. The numerical result shows a good scaling be havior.
Top-Charm Production in the Topcolor-Assisted Technicolor Theory
YUE Chong-Xing, LI Jian-Tao
2001, 25(10): 945-951.
In the framework of topcolor-assisted technicolor (TC2) theory, we calculate the contri- butions of TC2 dynamics and the neutral top-pion to top-charm production at the high energy e+e linear collider (LC) experiments. Our results show that the contributions mainly come from the neu- tral top-pion π0t. The cross section is of the order of 10-2 pb in most of the parameter space in the TC2 theory. If we assume that the integrated luminosity of LC experiments is 500fb-1, it would pro- duce serveal thousand events. So it is possible to detect the signature of TC2 theory at the future LC experiments.
Antiproton Spectrum Produced by Dark Matter Annihilation
SUN La-Zhen, LIU Yao-Yang, JIANG Xiang-Dong
2001, 25(10): 952-957.
The cross section of the process X-0X-0→gg is calculated in supersymmetry model of parti- cle physics. By means of the obtained cross section value, the estimate of source spectrum for anti- protons produced by neutralino X-0 annihilation is given. We conclude that the observation of this spectrum in the low energy region offers a possible approach to find the dark matter and the super- symmetry particle.
Trace Formula and Periodic Orbits Quantization for Two-Dimensional Integrable System
SONG Jian-Jun, LI Xi-Guo
2001, 25(10): 958-963.
The general quantization condition for periodic orbits in a two-dimensional integrable sys- tem is presented via the Berry-Tabor trace formula. Using the quantization and a periodicity condi- tion of periodic orbits the semiclassical quantization condition and semiclassical quantized energies of a two dimensional uncoupled quartic oscillator system are given in detail. The semiclassical quantized energies-periodic orbits correspondence is also analysed.
Antibunching Effect for the Eigenstate of the Higher Powers of the Annihilation Operator of Two-Parameter Deformed Harmonic Oscillator
WANG Zhong-Qing
2001, 25(10): 964-970.
The antibunching effect for the eigenstates of the k-th powers of the annihilation operator of two-parameter deformed harmonic oscillator (akqs,k≥3) is studied. Using the numerical method , we have studied the influences of the two parameter (qs) deformation on the effect in the case of k = 3. It is shOwn that the eigenstates of akqs have anibunching effect when x = |α|2,which reflects the intensity of the two-parameter deformed light field, is in values of certain intervals. The effect is evidently influeneed by the values of paratnters q and s.
Nuclear and ion Physics
Measurement of β+ Delay Proton Decay of 23Al
WANG Hong-Wei, JIN Gen-Ming, Wu He-Yu, ZHANG Bao-Guo, XIAO Zhi-Gang, DUAN Li-Min, WEI Zhi-Yong, LI Zu-Yu, LU Zhao-Hui, LIU Yong-Ying, CHEN Ke-Liang, HU Rong-Jiang, ZHU Hai-Dong, CEN Ling, WANG Su-Fang, LI Xiang-Qing, CHEN Tao, HUA Hui
2001, 25(10): 971-976.
The β+ delay proton decay spectrum has been measured with TOF-ΔE method and zero degree detectors at the radioactive ion beam line in Lanzhou. The half life of 23 Al was determined to be T1/2=(476±45)ms by using a time scaler cornbined with the precision pulse generator, which is consistent with the other group's result of (470±30)ms. The known β+ delay protons at Ed=0.216,0.278,0.438,0.479MeV have been observed in the experiment. A new energy level of23Mg at Ex=8.916MeV was found in the β+ delay proton decay of 23 Al, and their relative intensity was also determined.
High Spin States in the N=50 Nucleus 88Sr
LIU Zhong
2001, 25(10): 977-983.
Excited states of 88Sr have been produced in the fusion evaporation reaction between 82Se beam and 16O from a heavily oxidized Ba target and studied using the in-beam γspectroscopy tech- niques. Two high-spin level structures have been Observed and established up to 8.5MeV and 7.9MeV excitation energy with spin values of 13h and 12h, respectively. Based on the measure- ments of the DCO ratios and anisotropies of γ-rays, spin values of the excited states have been as- signed up to the highest levels observed. Possible coofgurations are discussed for the two high spin level structures.
Shape Change of 129Ce at High Spin States
LI Guang-Sheng, DAI Zheng-Yu, LIU Xiang-An, ZHANG Lan-Kuan, WEN Shu-Xian, WU Xiao-Guang, YUAN Guan-Jun, PENG Chao-Hua, WENG Pei-Kun, LI Sheng-Gang, YANG Chun-Xiang
2001, 25(10): 984-988.
High spin states of 129Ce were populated through the reaction 116Sn(16O,3n)129Ce at a beam energy of 73 MeV. Lifetimes of the excited states were measured using the Doppler shift atten-uation method. The transition quadrupole moments Qt were deduced from lifetime data. The results indicate that collectivity of 129Ce is reduced with respect to the even-even core 128Ce. This reduction in collectivity caused by the addition of a h11/2 neutron can be interpreted as due to triaxial deforma-tion induced by shape driving effect. Although the Qt values of the negaive-parity band are some-what smaller than the ones of the positive-parity band, they exhibit a considerably sindlar behavior with increasing angular momentum. It would appear that the two h11/2 quasiprotons possibly have a dominant innuence on property of the core.
Nuclear Deformation Effect on the J/ψ Suppression
SA Ben-Hao, LU Zhong-Dao, SU Zong-Di
2001, 25(10): 989-993.
The nuclear deformation effect on the J/ψ suppression in U-U central collisions at 200A GeV/c is investigated based on the hadron and string cascade model, JPCIAE. We found that the J/ψ suppression is nearly decreased by a factor of two, if the major axes of both deformed nuclei are changed from along the beam direction, to the perpendicular the beam direction.
Study on γ-Ray Strength Functions and Energy Spectra in the Neutron Radiative Capture of 197Au
LIU Jian-Feng, ZHAO Wei-Juan, WANG Feng-Ge, SU Zong-Di
2001, 25(10): 994-1001.
The aim of this paper is to explain theoretically the abnormal protuberances near and after 5.5 MeV in the gamma spectra of the (n, γ) reactions for the nulei in the regions of 110≤A≤140 and 180≤A≤210.
Supposing that in the primary and cascade gamma de-excitation processes of the compound nu- cleus, besides the giant dipole resonance model, there exist the deexcitation processes of the excited states of 6He,6Li,6Be,7Li and 7Be particle Clusters, the γ-ray strength function in which these pro- cesses are contained was constructed. The (n ,γ) reaction cross sections and the gamma energy spec- tra in the neutron incident energy region from 0.01 MeV to 3MeV for 197Au were calculated. The re- suIts are in better coincidence with the experiments. Especially for the gamma energy spectra, the abnormal protuberances near and after 5.5MeV were reproduced very well.
Distributions of Realative Momentum of Pion Pairs in Relativistic Heavy Ion Collisions
CHEN Xiao-Fan, CHEN Zhi-Lai, YANG Xue-Dong, LI Zhu-Peng
2001, 25(10): 1002-1005.
The distributions of the relative momentum of correlated and uncorrelated pion pairs are given. The relations between the parameters of elliptical and spherical pion sources are obained by using the distribution of the relative momentum of correlated pion pairs, and comparison is made with the experimental result of central relativistic heavy ion collisions 1. 8A GeV Ar+Pb. For higher tem- perature, the distribution of single-pion momentum p1(p)=N·exp(- m2+p2/T) should be used to obtain the results.
On the Moment of Inertia and Surface Redshift of Neutron Star
LI Wen-Fei, ZHANG Feng-Shou, CHEN Lie-Wen
2001, 25(10): 1006-1011.
Using temperature, density and isospin dependent nuclear equation of state, we calculat- ed the moment of inertia and surface redshift of neutron star by resolving Tolman-Oppenheimer-Volkoff equation. It is found that the moment of inertia and surface redshift strongly depend on the nuclear equation of state. The equation of state with high value of uncompressihility and symmetry en- ergy strength coefficient provides a big moment of inertia, while effective mass of nucleon has almost no effect on moment of inertia. Meanwile, the equation of state with high value of uncompressibility and effective mass of nucleon provides a big surface redshift, while the symmetry energy strength co- efficient has almost no effect on surface redshift of neurtun star. The relationship between moment of inertia and mass is also given in this paper. By comparing the calculated results with the one obtained sendempirically from astronomy, we find that a softer equation of state can provide a more reasonable result.
Detection Technology and Methods
Characteristics of the Transtion Curves of Showers and Discrimination of γ-Rays and Hadrons in Iron Emulsion Chambers
JI Xiao-Bin, FU Yu, XUE Liang, ZHANG Xue-Yao, LI Jie, LI Jin-Yu, ZHANG Nai-Jian, He Mao, REN Jing-Ru, LU Sui-Ling
2001, 25(10): 1012-1016.
The GEANT3 code, a general software for detector simulations widely used in the experi- ments of particle physics, is introduced to the Monte Carlo simulation of iron emulsion chambers. Some haracteristics of transition curves of cascade shower and their FWHM (Full Width of Half Maximum) are studied. The probability of discriaminating hadrons from gamma rays using the FWHM distributions for the shower events with starting depth Δt<6c. u. is discussed and an efficient joint criterion of discriminating hadrons from γ-rays in iron emulsion chambers is obtained.
Accurate Computation on High Order Modes of Axial-symmetric Cavity with Vector Finite Element Method
WEI Shi, LIN Yu-Zheng
2001, 25(10): 1017-1021.
Eigenfrequencies of high order modes in the axial-symmetric cavities are computed with a vector finite element method. Mathematics models and physics theories are combined in a rational way, which avoids the spurious modes caused by ordinary finite element methods. Using quadratic scalar and vector basis functions, high accuracy of results are available with few meshes. A code named Cafe is presented. It provides a good base for further research of wakefields of the detuned structures in next generation linear collider.
Effects of the Relativistic Electron Beam on the Phase Velocity of RF Field in Accelerator
PAN Wei-Min, LI Zhong-Quan, XIE Xi
2001, 25(10): 1022-1028.
The effects of the relativistic electron beam on the phase velocity of RF field in accelera-tor for small signal are studied. The idea of equating electron beam with medium is first developed and the formula of equivalent relative dielectric constant is derived. Based on this consideration and deduction, the simplified dispersion equation of disk-loaded waveguide with the relativistic electron beam under small signal field is established, by which the magnitude of the phase velocity variation of microwave field in accelerator with small signal can be obtained.
Production of Pulsed Ion Beams by ECR Ion Source Afterglow Mode
SONG Pei, GUO Xiao-Hong, ZHAO Hong-Wei, ZHANG Zi-Min, FENG Yu-Cheng, LI Jing-Yu, ZHANG Xue-Zhen
2001, 25(10): 1029-1034.
To satisfy the requirements of the Heavy Ion Cooling Storage Ring which is under con- struction at Lanzhou, afterglow mode was tested with the IMP 14 .5GHz ECR ion source to produce pulsed ion beams. The afterglow phenomenon was clearly observed and the pulsed ion beams of Ar11+ and Ar12+ were successfully produced with pulsed rf power. The peak current of the pulsed beam is typically two or three times higher than that of cw beam. The afterglow peak current could increase by a factor of six after further optiedzation during the experiment. The mechani8m of the af terglow mode was studied and discussed on basis of the test results and physical model of ECR ion source.