2005 Vol. 29, No. 04

Particle and field theory
Search for Exotic States at BESⅢ
MA Xu-Bo, FANG Shuang-Shi, ZHU Yu-Can, LU GoNG-Ru, YANG Hong-Xun
2005, 29(04): 329-336.
Abstract:
A general introduction to the theoretical predictions for the mass,width and decay modes of exotic states is briefly described. the current status of experiment searches for the candidates of exotic states and their inconsistences with theoretical predictions are are discussed Some specific J/ψ decays channels are proposed to search for exotic states at BESⅢ experiment.
On the Structure of Reggeon
PENG Hong-An, HE Zhen-Min, GAO Yong-Hua, YAN Zhan-Yuan, DUANG Chun-Gui
2005, 29(04): 337-344.
Abstract:
Starting from the point-view that the constituent quark has its own inner structure and according to the hypothesis of the maximum non-perturbative strong interaction reaction which should be obeyed in high energy strong-soft Processes ,we proposed a structure model of the Reggeon(R). In such processes a pair of constituent quark-antiquark in colliding hadrons would individually desociate with certain probahility into a non-perturbative gluon and a spinor-like cluster firstly. The spinor-like clusters will further emit non-perturbative gluons and then annihilate each other. Corresponding to such mechanism the relevant structure of R in the field theory can be represented by summing over a set of cutting ladder diagrams, where the vertical lines are the propagators of spinor-like clusters and the rungs are non-perturbative gluons. In the multi-Regge region where the energy of the system is very large and its momentum transfer│t│is very small, under the approximation that only the leading order logarithm terms of s are preserved, the scattering amplitudes for these cutting ladder diagrams are derived and summed. Thus, a compact formula of the typical Regge pole trajectory of mesons which are composed of light quarks is obtained.
Higher Order RPA Calculation of the Glueball Wave Function in 2+1-D SU(2) LGT
HUI Ping
2005, 29(04): 345-349.
Abstract:
By Solving Shrodinger equation with the RPA coupled cluster method, The higher order glueball wave function in 2+1-D SU(2) lattice gauge theory is calculated. In the calculation, hollow Wilson graphs are selected as the trial wave function, and special Wilson graphs are treated approximately. The sixth and the seventh order results for the coefficients μ0F andμ2F and the relevant parameterζ of the glueball wave function show good scaling behaviors at weak coupling region(β=4.8--9.6 ). The seventh order vacuum energy curve is in agreement with the sixth order ones for in the coupling region of β=0.8-8.8 .
Calculation and Generalization of Non-Adiabatic Geometric Phase of Isotonic Oscillator with Operator Decomposition
An Nan, YANG Xin-E
2005, 29(04): 350-353.
Abstract:
Operator decomposition approach is used to calculate the non-adiabatic geometric phase of anharmonic oscillator. As an example we focus on isotonic oscillator, a type of anharmonic oscillator. The Aharonov-Anandan phase is derived when we choose base state and the first excitation state as cyclic initial states. Then we generalize our result by choosing three states or more states as cyclic initial states. Finally we give an general formula of Aharonov-Anandan phase for time-independent systems and discuss its applicability.
Nuclear and ion Physics
Effect of Pairing Correlation on the Ground State and Collective Excitations of Nucleus
CAO Li-Gang, MA Zhong-Yu
2005, 29(04): 354-360.
Abstract:
The contribution of the resonant continuum to pairing correlations is properly treated in the RMF+BCS approximation with a constant pairing strength. The results show that the contribution of the proper treatment of the resonant continuum to pairing correlations for those nuclei close to neutron drip line is important. The quasiparticle relativistic random phase approximation (QRRPA) is applied to investigate the collective excitations of open shell nucleus. The numerical calculations are performed in the case of various isoscalar giant resonances of nucleus 120Sn. The calculated results show that the QRRPA approach could satisfactorily reproduce the experimental data of the energies of low-lying states.
A Study of the Charm-Baryonic Structure from ㄚ Decays
PING Rong-Gang, ZOU Bing-Song
2005, 29(04): 361-365.
Abstract:
In the framework of perturbative QCD,the exclusive decays $\Upsilon\to B\bar B$(B:baryon) are studied.With the constituent quark model describing the charm-baryonic structure, we calculate the decay widths for $\Upsilon\to p\bar p,\Lambda_c\bar \Lambda_c,\Sigma_c\bar \Sigma_c,\Xi_c\bar \Xi_c,\Xi_{cc}^+\Xi_{cc}^-,\occc\bar \occc $ , and discuss the prospect to search for the charm baryon $\occc$ in $\Upsilon$ decays.
Study on Stiffness of the Symmetry Energy at High Densities by π+ Ratio
YONG Gao-Chan, Bao An Li, ZUO Wei
2005, 29(04): 366-370.
Abstract:
using the isospin–and momentum–dependent transport model, for three different symmetry energies, we have calculated the π+ ratio as a function of time and tranverse–momentum in central 132sn+124 sn collision at e_beam/A=400mev. the results show that the π+ ratios is very sensitive to the stiffness of the symmetry energy. thus we can probe the stiffness of the symmetry energy at high densities by using the π–/π+ ratio at different time or transverse momentum more accurately than before. comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.hadronic transport model, symmetry energy, π–/π+ ratio
Study on the Feature of Longitudinal Collective Flow Distribution and Nuclear Stopping at RHIC
YUAN Xian-Bao, FENG Sheng-Qin
2005, 29(04): 371-375.
Abstract:
The net–proton distribution features at rhic have been analyzed by using non–uniform flow model in this paper. it is found that the system produced at the rhic energy region has stronger non–uniform feature than at the ags and sPs energy regions, which means that nuclei at rhic energy region is much more transparent. it is shown that our analysis relates closely to the study of nuclear stopping of experiment. and then, the proton,anti–proton and net–proton distributions are studied , respectively. this investigation help us to understand the feature of particle stopping in the newest rhic experiment.
Detection Technology and Methods
Physical Design of Main Drift Chamber Trigger for BESⅢ Experiment
XU Hao, LIU Zhen-An, JIN Da-Peng, WANG Da-Yong, ZHAO Di-Xin, GUO Ya-Nan
2005, 29(04): 376-382.
Abstract:
this article describes the design and simulation of the scheme of main drift chamber (mdc) trigger for besⅢ (beijing spectrometer Ⅲ). the algorithm of mdc trigger includes 3 steps: track segments finding (tsf), track finding (tf) and trigger condition formation of mdc tracks. these trigger conditions are studied carefully and the trigger parameters are optimized through simulation. trigger efficiencies vs. p_t ,vertex position r–φ and z are presented. trigger efficiency exceeds 99% for J/ψ events and some important physics channels. the rejection of beam–related backgrounds exceeds 99.99% and the rate of cosmic rays is about 18hz.
Development of Si Multi-Strip Detector
TAN Ji-Lian, JIN Gen-Ming, WANG Hong-Wei, DUAN Li-Min, YUAN Xiao-Hua, WANG Xiao-Bing, LI Song-Lin, LU Zi-Wei, XU Hu-Shan, NING Bao-Jun, TIAN Da-Yu, WANG Wei, ZHANG Lu
2005, 29(04): 383-386.
Abstract:
the technics and test results and preliminary applications of si multi–strip detector fabricated by using microelectronic technique were described in this paper. the sensitive area of this kind of detector is 50mm×20mm. the P side surface was divided into equal 16 strips with 140μm spece between two strips ,each one having length of 20mm and width of 3mm. a reverse leakage current less than 2na and an energy resolution of 0.4%–0.9% (for 239 Pu α particles) and a crosstalk between neighboring strips of 4%–8% have been obtained when the detector was operated in full depletion condition. an energy resolution of ~0.27% was achieved for measuring of 7.2mev/u c ions.
Experimental Study of a Small-Cell drift Chamber Operated with Helium-Based Gases
LIU Jian-Bei, CHEN Chang, CHEN Yuan-Bai, JIN Yan, LIU Rong-Guang, MA Xiao-Yan, MA Yuan-Yuan, QIN Zhong-Hua, TANG Xiao, WANG Lan, WU Ling-Hui, XU Mei-Hang, ZHU Min
2005, 29(04): 387-392.
Abstract:
The performance of a small–cell drift chamber operated with two helium–based gas mixtures, he/c_3h_8(60/40) and he/ch_4(60/40), was studied using cosmic rays, respectively. the gas mixture ar/co_2/ch_4(89/10/1) was also tested for comparison. the spatial resolution and de/dx resolution of the helium–based gases are better than those of ar/co_2/ch_4(89/10/1). a good spatial resolution of 110μm and a de/dx resolution of 6%–7% with 30–40 samples were obtained with he/c_3h_8(60/40).
Time Performance Study on Precision Drift Tube at High Pressure
OU Yang-Qun, ZHUANG Xu-Ai, XIE Yi-Gang, ZHENG Shu-Chen, CHI Shao-Peng, XIE Song, HAN Hong-Guang, CHENG Shao-Chen, YANG Yi
2005, 29(04): 393-398.
Abstract:
In this paper the time performance of the precision drift tube at high pressure has been studied. the time spectrum of the drift electrons and the (r–t) relationship between the distance from the charged particle track to the anode wire and the drift time have been measured via both radioactive sourceand cosmic rays. some factors which influence the r–t relationship have been also investigated. the fitting parameters of the drift time spectrum have been analyzed and the r–t relationship has been obtained from the drift time spectrum by using integral method.
Thin Plastic Scintillating Foil for Measuring Pulsed Neutron Flux in High Gamma-Ray Environment
OUYANG Xiao-Ping, LI Zhen-Fu, WANG Qiu-Shu, HUO Yu-Kun
2005, 29(04): 399-403.
Abstract:
A new conception of measuring pulsed neutron flux in high gamma–ray environment with a thin plastic scintillating foil is presented. based on the calculations of the response to neutrons and gamma–rays, a new gamma–insensitive detector for detecting fast rising, transient neutron flux has been developed and preliminarily tested, which comprises a thin plastic scintillating foil of st401 (tPsf) and a photomultiplier tube (or a photodiode). the detector exhibits three distinct properties compared with the conventional ones: (1) high neutron sensitivity, (2) high n/γ discrimination, and (3) flat response in the given neutron energy range.
Accelerator
Development of the BEPCⅡ Positron Source Flux Concentrator
LIU Jin-Tong, GEN Zhe-Qiao, SUN Xian-Jing, SUN Yao-Lin, PEI Guo-Xi
2005, 29(04): 404-407.
Abstract:
The flux concentrator is a matching device for the positron beam, which matches the transverse emittance between the target and successive accelerator tubes. it is one of the most important parts of the bePcⅡ positron source and for improving the positron catching efficiency. based on the design and the manufacture of the flux concentrator, we studied the distribution of the magnetic field and the resonance property of the flux concentrator by computer simulation and compared the results with those of experiment.
2-D Beam Profile Measurement Based on CT Algorithm with Rotating Multi-Wire Target
YU Neng-Jie, TANG Chuan-Xiang, ZHENG Shu-Xin, LI Quan-Feng, GONG Ke
2005, 29(04): 408-412.
Abstract:
A new method for the 2–d low energy electron beam profile measurement is developed. based on the ct(computer tomography) algorithm, multi sets of data about the 1–d beam profile projections are attained by rotating the multi–wire target. then a 2–d beam profile is reconstructed from these projections with ct algorithm. the principle of this method is analyzed theoretically in detail and the initial facilities for the experiment with some results are presented.
Lorentz Force Detuning Analysis of 700MHz Single-Cell Superconducting Cavity
GE Ming-Qi, ZHAO Sheng-Chu
2005, 29(04): 413-417.
Abstract:
In this paper, the lorentz force detuning of superconducting cavity is illustrated and discussed in detail. the static lorentz force detuning and dynamic lorentz force detuning of a 704mhz/β=0.45 single–cell superconducting cavity is calculated with numerical simulation method. and the mechanical stability of the cavity is also studied. finally a method for stiffening cavity is proposed.
Coupling Compensation Scheme in BEPCⅡ
YU Cheng-Hui, WU Ying-Zhi, XU Gang
2005, 29(04): 418-423.
Abstract:
A new idea to compensate the coupling of bePcⅡ will be introduced in this paper. the detector solenoid field in the interaction region will be compensated by six anti–solenoids which are located nearby the interaction point. skew quadrupoles are adopted for the global coupling compensation. the coupling compensation scheme and the method to measure and tune the x–y coupling will be discussed in detail.
Application of Data Mining in Beam Status Descriptive Modeling
XIE Dong, LI Wei-Min, XUAN Ke, HE Duo-Hui
2005, 29(04): 424-429.
Abstract:
cluster analysis is an effective method for describing colony character. hower, as the size of mined databases increased ,it is a complex problem in searching for the extremum of score function. in this paper, we propose a novel technique and apply it in beam current descriptive modeling. our experiments show that the method is quick and efficient .as reproducibility is an important specific of a storage ring, the clustering model is helpful for machine study and decision–making.
Synchrotron radiation,applications of nuclear techniquees,etc
VUV/EUV Primary Standard Detector Facility and Transfer Detector Calibration
ZHENG Lei, CUI Ming-Qi, ZHAO Yi-Dong, ZHU Jie, ZHOU Ke-Jin, CHEN Kai, ZHAO Jia, SUN Li-Juan, MA Chen-Yan, ZHOU Hong-Jun, HUO Tong-Lin
2005, 29(04): 430-434.
Abstract:
A transfer standard detector was calibrated for the fist time with respect to the vuv/euv primary standard detector built at the metrology beamline in national synchrotron radiation laboratory (nsrl) at wavelength 17.625nm, 6.8nm and 92nm. the repetitively calibrated quantum efficiencies for si photodiode are in good agreement at each wavelength with the relative accuracy of 1%–14%. but compared with the quantum efficiency from nist, our result has good agreement at wavelength 17.625nm while poor agreement at wavelength 6.8nm and 92nm. the stability of the light source and the spectral impurity has significant effect on calibration.
Evolution of Field Entropy in the Multiphoton Jaynes-Gummings Model
LU Dao-Ming
2005, 29(04): 435-438.
Abstract:
In this paper, the dynamical properties of the field entropy in the multiphoton jaynes–cummings model are studied. it is showed that the evolution of field entropy has no periodicity and is influenced by the initial states of atoms and the initial phase of the field.