2007 Vol. 31, No. 6

Particle and field theory
Study of p-Air Inelastic Cross Section with Directly Arrived Protons at Yangbajing
LAN Xiao-Gang, HOU Yan, ZHOU Xun-Xiu, JIA Huan-Yu, CAO Zhen, DING Lin-Kai
2007, 31(6): 513-517.
A method of determining the p-air inelastic cross section by measuring the directly arrived protons at high altitudes is presented. Its feasibility is studied via a Monte Carlo simulation. Assuming a KASCADE-like hadron calorimeter is set up at the center of the Yangbajing ARGO array, selecting events with air shower (AS) cores hitting the calorimeter, using the full-coverage ARGO array as AS anti-coincidence and using the calorimeter to measure energies of the unaccompanied hadrons, the directly arrived primary protons can be registered with a known efficiency. By the obtained event sample of directly arrived protons the p-air inelastic cross section used in the Monte Carlo can be re-produced with a precision of 1%—2% that demonstrates the feasibility of this approach.
Measurement of Strong Coupling Constant at Low Energy Range
HU Jun-Hui, WENG Yao, HU Hai-Ming, YANG Yong-Xu, GAO Yuan-Ning, WANG Jun
2007, 31(6): 518-522.
The strong coupling αs(s) is an important free parameter of Quantum Chromodynamics. Based on R values measured at BES, the values of the strong running coupling constant αs(s) at 2.0—3.7GeV are determined using the O(α3s) and O(α4s) order expressions calculated by pQCD, then αs(s) is deduced to the Mz scale. The numerical prediction on the improvement of the uncertainty of αs(s) with the decrease of the experimental error of R value in the future experiment is also given.
Perturbative QCD Study of B(s)→φρ Decays
LI Jing-Wu, YOU Fu-Yi
2007, 31(6): 523-531.
We study B(s)→φρ decays in a perturbative QCD approach based on kT factorization. In this approach, we calculate factorizable and non-factorizable contributions, there are no annihilation contributions due to quark content. We get the branching ratios and polarization fractions for B(s)→φρ decays. Our predictions are consistent with the current experimental data.
particle and nuclear astrophysics and cosmology
Effect of σ*,φ Mesons on the Neutron Star Matter at Finite Temperature
ZHAO Xian-Feng, WANG Shun-Jin, ZHANG Hua, JIA Huan-Yu
2007, 31(6): 532-537.
Within the RMF approach, considering the contribution of σ*,φ mesons and baryon octet {n,p,Λ,Σ0+0}, some properties of neutron star matter have been investigated in the temperature region between 5—15MeV. It is found that when the contributions of σ*,φ mesons are included, (1) the critical baryon density decreases (but for the Λ hyperon, the effect is not obvious), but the number of hyperons increases; (2) the equation of state becomes soft at higher energy density; (3) the maximum mass decreases while the corresponding radius increases; (4) the central density, the central energy density, and the central pressure all become smaller. At T=5MeV and 10MeV and for Σ00+, the σ*,φ mesons make critical baryon density greatly decrease; but at T=15MeV, 20MeV, and 25MeV, the effect is not obvious. However, for Λ,Σ hyperons, at all the above temperatures, the effect is not obvious.
Nuclear and ion Physics
Simulation Study on the Splitting Effect of Transverse Mass Spectra in p+p Collisions at √S=200GeV Using PYTHIA
XU Yi-Chun, SHAO Ming, ZHANG Zi-Ping
2007, 31(6): 538-542.
In proton-proton (p+p) collisions at √S=200GeV, it is found that the previously observed universal shape of transverse mass spectra of hadron production seems to break down into two species of baryons and mesons at higher transverse mass region. In order to understand the underlying physics mechanism, a Monte Carlo study is done using the PYTHIA event generator. The simulation results demonstrate that this difference exists not only within string fragmentation scheme but also within independent fragmentation scheme, and comes primarily from gluon jets within string fragmentation scheme at RHIC energy. The new introduced physics mechanisms in PYTHIA version6.3 indicate that the complicated string junction may contribute to this splitting effect between mesons and baryons.
Study of Nuclear Level Structure in Tc Isotopes with Mass A~100
SHEN Shui-Fa, WANG Feng-Ge, FANG Ke-Ming, XU Fu-Rong
2007, 31(6): 543-547.
In the present work, the structures of the excited positive/negative-parity yrast states of 101Tc are discussed by using a projected shell model, and a band diagram calculated for the positive-parity yrast band is also shown in order to extract physics out of numerical results. In addition, the analysis of other three bands originated from 3/2[301], 5/2[303], and 1/2+[431] Nilsson states, respectively, is also performed in the framework of this model. Until recently, very little property about the N=52—54 intermediate nuclei in the Z~42—44 region has been known. In order to understand these "transitional nuclei", we select the nucleus 95Tc as an example. So in this work, we also present our investigation of the level structure in the 95Tc nucleus.
Investigation of Radioactivity of Uranium Target in Target-Source of ISOL
YAN Fang, CUI Bao-Qun, SHU Neng-Chuan, LIU Ting-Jin, WU Hai-Cheng, FAN Sheng
2007, 31(6): 548-552.
The variety of radioactivity and gamma intensity with time in uranium target of ISOL target-source system under irradiation by 100MeV, 200μA high intensity proton beams has been calculated by using three methods, and the results will provide some dosimetric reference for the design, exchange and disposal of target.
Influence of System Size Dependence of Energy Loss on Hadron Spectra Suppression
WANG Xiao-Dong, ZHANG Han-Zhong, WANG En-Ke
2007, 31(6): 553-557.
Based on parton model in QCD, at the leading-order approximation we studied the π0 spectra and nuclear modification factor RAA in Au+Au and Cu+Cu collisions with different centralities. Because of parton jet energy loss in heavy ion collision, large transverse momentum hadrons spectra are suppressed as compared to p+p collisions at the same energy. It is shown that the suppression has strong dependence on the system size which determines the amount of the jet energy loss. The bigger the system is, the larger parton energy loss is. It results in the much more suppression of the spectra and also the much less RAA.
Systematic Analysis of E(5) Critical-Point Nuclei in A~130 Region with Relativistic Mean Field Theory
SHENG Zong-Qiang, GUO Jian-You, MENG Ying
2007, 31(6): 558-563.
The shape phase transition between spherical U(5) and γ-unstable O(6) nuclei is investigated systemically for the nuclei in the A~130 region by the constrained relativistic mean field theory. By examining potential energy surfaces and neutron Fermi energies, we suggest that 136Ba and 132,134Xe are possible nuclei with E(5) symmetry, which is favored by the observed ratio R4/2=(E+41-E+01)/(E+21-E+01). While the RMF predicted E(5) symmetry or 128,130,132Te cannot be supported by the observed ratio R4/2. Whether these nuclei are critical-point nuclei should further be examined in experiments.
Detection Technology and Methods
Status of ULE-HPGe Detector Experiment for Dark Matter Search
LI Xin, YUE Qian, LI Yuan-Jing, LI Jin, HE Dao, KIM S, KWAK J, ANG H
2007, 31(6): 564-569.
An Ultra Low Energy HPGe (ULE-HPGe) detector, with CsI (Tl) active shielding, is applied to the direct detection experiment for weakly interacting massive particles (WIMP), and located in Korea. The setups for the whole system and the calibration have been completed and more than half a year's background data have been accumulated. Some external neutron and gamma source experiments were carried out to study the origin of the background. The analysis and preliminary results are shown, and an attractive future is also provided.
Pattern-Matching Track Reconstruction for the BESⅢ Main Drift Chamber
ZHANG Yao, ZHANG Xue-Yao, LI Wei-Dong, MAO Ze-Pu, MA Qiu-Mei, MA Xiang, WANG Liang-Liang, WANG Ji-Ke, DENG Zi-Yan, YOU Zheng-Yun, WEN Shuo-Pin, BIAN Jian-Ming
2007, 31(6): 570-575.
The tracking algorithm, MdcPatRec, is developed for the Drift Chamber of the BESⅢ detector using C++ language and object-oriented techniques. This algorithm uses a pattern matching method to find track segments and then combine them into track candidates followed by a least square fit. With the simulation data, the tracking performances such as efficiencies and momentum resolution have been studied and results are consistent with parameters from detector design. The algorithm is also proved to be robust enough to process data with severe background expected by the BESⅢ experiment.
Study on MRPC-TOF Timing Properties and Calibration Methods
LI Liang, SHAO Ming, CHEN Hong-Fang, LI Cheng, TANG Ze-Bo, DONG Xin, WANG Xiao-Lian
2007, 31(6): 576-580.
A prototype Time-of-Flight (TOF) detector, consisting of 28 Multi-gap Resistive Plate Chambers (MRPC), has been successfully operated at RHIC-STAR experiment since 2003. Extensive study on the calibration procedure of the MRPC-TOF is performed in order to better understand MRPC's performance. Improvements and extension on current calibration method are discussed. Furthermore, it has been found that the position resolution of the reconstruction system at STAR has significant impact on the MRPC time resolution. After subtracting this effect, the intrinsic time resolution of MRPC is found to be about 60ps, which is in good agreement to beam test results.
Study of the LED Based Light Calibration System for Neutron Wall Detector
YU Yu-Hong, XU Hua-Gen, ZHAN Wen-Long, XU Hu-Shan, SU Hong, LI Xiao-Gang, SUN Zhi-Yu, XIAO Zhi-Gang, HU Zheng-Guo, GUO Zhong-Yan, WANG Jian-Song, CHEN Ruo-Fu, FAN R
2007, 31(6): 581-585.
The light calibration system is one of the key components of Neutron Wall detector. It is used to calibrate the electronics and to monitor the long-term stability of the detector modules. With the detaile investigations, a calibration system with high-power LED (3W) driven by the fast pulses has been carried out. It is also tested together with the detector module of the Neutron Wall and the result of the preliminary calibration demonstrates that it fulfills the needs. It's a new design proposal to the light calibration system of the fast scintillator detector.
Application of Frequency Map Analysis to the BEPCⅡ Lattice
JIAO Yi, ZHOU De-Min, WANG Jiu-Qing, QIN Qing, XU Gang, FANG Shou-Xian
2007, 31(6): 586-592.
The frequency map analysis (FMA) method is systematically applied to the lattice of the BEPCⅡ storage ring for the first time in this paper. We compute characteristic parameters of the lattice with the Accelerator Toolbox (AT) code, in which the FMA method is imbedded, and compare the results with those of MAD and SAD codes. The lattices of the BEPCⅡ collision and injection modes are analyzed and optimized using FMA with the RF cavity and radiation on. Both on- and off-momentum frequency maps are studied to have a complete picture of dynamics. The synchro-betatron resonance is found to have large effect on the beam dynamics.
Research on Multi-pulsed High Intense Electron Vacuum Diode
XIA Lian-Sheng, WANG Wen-Dou, MOU Fan, ZHANG Huang, CHEN De-Biao, ZHANG Kai-Zhi, SHI Jin-Shui, DENG Jian-Jun, ZHANG Lin-Wen
2007, 31(6): 593-596.
There are some differences between the single pulsed vacuum diode and the multi-pulsed vacuum diode. When vacuum diode is working under multi-pulsed mode, cathode plasma changes the designed condition inevitably. Formulas are presented in the paper to describe the vacuum while it is working under multi-pulsed mode. Simulation is used to describe cathode plasma explosion behavior. A column explosion mode is adopted in the paper while simulating cathode emitting. Experiments are also undertaken to study the characteristics of electron beams generated by a double pulsed intense electron diode with velvet cathode. When the diode pulsed voltages are 700kV, the beams' brightness is better than 1×108A/(m.rad)2 and the two beams' envelope changes little during beams' extraction process.
Synchrotron radiation,applications of nuclear techniquees,etc
Double Laue-Crystal Monochromator for an X-Ray Imaging Beamline with Synchrotron Radiation
HU Wen, XIE Hong-Lan, DU Guo-Hao, XIAO Ti-Qiao
2007, 31(6): 597-601.
A new optical configuration of monochromator for X-ray imaging beamline, which allows one to obtain a parallel monochromatic beam with fixed exit by using two asymmetrically cut bent-crystals in Laue geometry, has been proposed. Based on the W14 multi-pole wiggler at SSRF, a preliminary design for the monochromator has been presented. The tunable photon energy range is 19—120keV, the flux output and flux density is 1.9×1013phs/s@33keV and 3.8×1010phs/s/mm2@33keV respectively. The flux and energy resolution of the monochromator is estimated, which indicates that the heat-load is tolerable and the design meets the demands of the X-ray imaging experiments. The results show that the new configuration of monochromator, compared with traditional design in double flat-crystal, is more powerful in dealing with the high flux and high heat-load.
Polarization Measurement of 3W1B Beamline at BSRF in Soft X-Ray Range
ZHU Jie, CUI Ming-Qi, SUN Li-Juan, WANG Zhan-Shan, ZHENG Lei, ZHAO Yi-Dong, ZHAO Jia, ZHOU Ke-Jin, CHEN Kai, MA Chen-Yan
2007, 31(6): 602-606.
Using Mo/Si multilayers as the polarizer and analyzer, we have measured the state of polarization for 86—89eV of Beamline 3W1B at Beijing Synchrotron Radiation Facility (BSRF). From the obtained data, we have determined the polarization parameters of Beamline 3W1B. Its polarizance is higher than 98% and the degree of circularly polarized radiation is between 1%—3% over a range of 86---89eV after polarizer.