2008 Vol. 32, No. 11

Particle and field theory
Search for exotic state 1-+ π1(1400) at BESⅢ
ZHANG Zhen-Xia, LIU Hong-Bang, WU Ning, YU Guo-Wei, SHEN Xiao-Yan, ZHENG Han-Qing
2008, 32(11): 857-861. doi: 10.1088/1674-1137/32/11/001

The J/ψ hadronic decays provide good laboratory to search for the hybrid states with exotic quantum numbers. A full Partial Wave Analysis (PWA) is performed to the generated Monte Carlo J/ψ→ρηπ data, based on the design of BESⅢ detector, to study the sensitivity of searching for a possible exotic state at BESⅢ.

A note on the mass splitting of K*(892)
GAO Dao-Neng, YAN Mu-Lin
2008, 32(11): 862-864. doi: 10.1088/1674-1137/32/11/002

Belle Collaboration reported a new observed value of K*-(892) mass by studying τ→ K-ντ decay, which is significantly different from the current world average value given by Particle Data Group 2006. Motivated by this new data, we revisit the issue on the K*0(892)-K(892) mass splitting. Our theoretical estimation favors the new measurement by Belle Collaboration. Therefore further experimental efforts are urgently needed to improve our understanding of these issues.

Angular momentum of a brane-world model
JIA Bei, LI Xi-Guo, ZHANG Peng-Ming
2008, 32(11): 865-867. doi: 10.1088/1674-1137/32/11/003
In this paper we discuss the properties of the general covariant angular momentum of a five-dimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of the inflationary RS model are all zero while the others are non-zero, which agrees with the results from ordinary RS model.
particle and nuclear astrophysics and cosmology
An updated search of steady TeV γ-ray point sources in northern hemisphere using the Tibet air shower array
WANG Yue, BI Xiao-Jun, CUI Shu-Wang, DING Lin-Kai
2008, 32(11): 868-872. doi: 10.1088/1674-1137/32/11/004

Using the data taken from Tibet II High Density (HD) Array (1997 February—1999 September) and Tibet-III array (1999 November—2005 November), our previous northern sky survey for TeV γ-ray point sources has now been updated by a factor of 2.8 improved statistics. From 0.0° to 60.0° in declination (Dec) range, no new TeV γ-ray point sources with sufficiently high significance were identified while the well-known Crab Nebula and Mrk421 remain to be the brightest TeV γ-ray sources within the field of view of the Tibet air shower array. Based on the currently available data and at the 90% confidence level (C.L.), the flux upper limits for different power law index assumption are re-derived, which are approximately improved by 1.7 times as compared with our previous reported limits.

Nuclear and ion Physics
A formula used to subtract the effect of gamma-ray of the others to that ofmeasured reaction in measurement of cross section of nuclear reaction andits application
ZHOU Feng-Qun, YANG Xing-Qiang, WANG Wei-Feng, LI Yong, ZHANG Fang, TUO Fei, KONG Xiang-Zhong
2008, 32(11): 873-876. doi: 10.1088/1674-1137/32/11/005
According to the regulation of growing and decay of artificial radioactive nuclide, a formula used to subtract the effect of characteristic γ-ray of the others to that of measured reaction was deduced. And then the cross sections of 120Te (n,2n)119mTe reaction induced by neutrons around 14~MeV were measured by activation relative to the 93Nb (n, 2n) 92mNb. In the process of the cross sections measured to be calculated, it was subtracted that the effect of characteristic γ-ray of 126Te (n, p) 126Sb to that of measured 120Te (n, 2n) 119mTe reaction using the formula deduced. The experimental results were (689±37) and (750±41) mb at the neutron energies of (13.5±0.3) and (14.6±0.3)MeV, respectively. Measurements were carried out by γ-detection using a coaxial HPGe detector. As samples, spectroscopically pure tellurium powder has been used. The fast neutrons were produced by the T(d, n)4He reaction. The neutron energies in these measurements were determined by the method of cross-section ratios between 90Zr (n, 2n) 89m+gZr and 93Nb (n, 2n) 92mNb reactions.
Analytical and statistical calculation of gamma dose rate for the accident of losing the shield for Tehran Research Reactor
Farshid Tabbakh, Azim Ahmadinyar
2008, 32(11): 877-881. doi: 10.1088/1674-1137/32/11/006

In this paper we study the analytical and statistical results of estimating the gamma dose rate at pool access floor in TRR when the core shield accidentally decreases to some non-permitted levels. Due to the risk of experimental techniques, we use the analytical and statistical methods. In normal conditions (no risk), the discrepancies between experiment and two methods are justified and it is found that for such problems we have to normalize these methods to experimental results as follows: the analytical method by factor 0.13 and MCNP by 1.7.

Shell evolution at N=20 in the constrained relativistic mean field approach
SUN Bao-Hua, LI Jian
2008, 32(11): 882-885. doi: 10.1088/1674-1137/32/11/007

The shell evolution at N=20, a disappearing neutron magic number observed experimentally in very neutron-rich nuclides, is investigated in the constrained relativistic mean field (RMF) theory. The trend of the shell closure observed experimentally towards the neutron drip-line can be reproduced. The predicted two-neutron separation energies, neutron shell gap energies and deformation parameters of ground states are shown as well. These results are compared with the recent Hartree-Fock-Bogliubov (HFB-14) model and the available experimental data. The perspective towards a better understanding of the shell evolution is discussed.

A systematic study of the superdeformation of Pb isotopes with relativistic mean field theory
GUO Jian-You, SHENG Zong-Qiang, FANG Xiang-Zheng
2008, 32(11): 886-891. doi: 10.1088/1674-1137/32/11/008

The microscopically constrained relativistic mean field theory is used to investigate the superdeformation for Pb isotopes. The calculations have been performed with the four different interactions NL3, PK1, TM1 and NLSH, and show that there exists a clear superdeformed minimum in the potential energy surfaces. The excitation energy, deformation and depth of the well in the
superdeformed minimum are comparable for the four different interactions. Furthermore the trend for the change of the superdeformed excitation energy with neutron number is correctly reproduced. The calculated two-neutron separation energy in the ground state and superdeformed minimum together with their differences are in agreement with the available data. The larger energy difference appearing in the superdeformed minimum reflects a lower average level density at superdeformations for Pb isotopes.

Cold nuclear matter effects on J/ψ production in d-Au collisions
WANG Hong-Min, HOU Zhao-Yu, SUN Xian-Jing
2008, 32(11): 892-896. doi: 10.1088/1674-1137/32/11/009

The medium modifications of J/ψ production in d-Au collisions at √sNN=200 GeV are studied in the Glauber model. By means of the c.m. energy loss parameter per collision studied in Drell-Yan process, taking account of the inhomogeneous shadowing effect, we find that the initial-state energy loss effect can be ignored in d-Au collisions at mid-rapidity. Then, the final-state J/ψ absorption effect is also considered and the theoretical results are in good agreement with the recent experimental data given by PHENIX. Finally, the experimental results of J/ψ production in d-Pb collisions are also predicted at RHIC and LHC energies respectively.

Two-pion interferometry in heavy ion collisions at HIRFL-CSR energy
YU Li-Li, ZHANG Wei-Ning, HUO Lei, ZHANG Jing-Bo
2008, 32(11): 897-902. doi: 10.1088/1674-1137/32/11/010

We examine the two-pion Hanbury-Brown-Twiss (HBT) interferometry for the particle-emitting source produced in heavy ion collisions at HIRFL-CSR energy. The source evolution is described by relativistic hydrodynamics with three kinds of equations of state for chemical equilibrium (CE), chemical freeze-out (CFO), and partial chemical equilibrium (PCE) models, respectively. We investigate the effects of particle decay, multiple scattering, and source collective expansion on the two-pion interferometry results. We find that the HBT radii of the evolution source for the CFO and PCE models are smaller than that for the CE model. The HBT lifetime for the CFO model is smaller than those for the PCE and CE models. The particle decay increases the HBT radius and lifetime while the source
expansion decreases the HBT radius. The multiple scattering effect on the HBT results can be neglected based on our model calculations.

Detection Technology and Methods
Design and experimental study of a two-dimensional position sensitive X-ray detector
WANG Xiao-Hu, ZHU Qi-Ming, CHEN Yuan-Bo, CHEN Chang, LIU Rong-Guang, WANG Lan, JIN Yan, MA Xiao-Yan, JIANG Shan
2008, 32(11): 903-907. doi: 10.1088/1674-1137/32/11/011

A prototype of a two-dimensional position sensitive X-ray detector was designed and constructed for small angle X-ray scattering experiments at BSFR (Beijing Synchrotron Radiation Facility). The detector is based on MWPC with cathode strip readout, and has a sensitive area of 200 mm×200 mm. The spatial resolution (FWHM) of about 210 μm along the anode wire direction was obtained from the 55Fe X-ray test of the detector.

Design and assembly of the CsI(Tl) crystal module of the BESⅢ electro-magnetic calorimeter
DONG Ming-Yi, CAI Xiao, FANG Jian, HU Tao, LAI Yuan-Fen, LIU Chun-Xiu, LÜ Jun-Guang, LIU Wan-Jin, SHANG Lei, SUN Li-Jun, WANG Zhi-Gang, XIA Xiao-Mi, YU Bo-Xiang, ZHOU Li
2008, 32(11): 908-911. doi: 10.1088/1674-1137/32/11/012

The CsI(Tl) crystal modules of the Beijing Spectrometer Ⅲ (BESⅢ) electro-magnetic calorimeter (EMC) were designed and assembled through Monte Carlo simulation and experiments. After the assembly was finished, the performance of each crystal module was tested by cosmic rays. All crystal modules were found to work well before the installation of EMC.

Experimental study of multi-photon contamination on the measurement offluorescent decay time
ZHU Wen-Han, ZHAO Yan-E, ZHANG Yun-Long, XU Zi-Zong, WANG Xiao-Lian
2008, 32(11): 912-915. doi: 10.1088/1674-1137/32/11/013

In the measurement of fluorescent lifetime based on time correlation-single photon counting technique by means of TAC, due to the contamination of multi-photons a deviation of fluorescent lifetime measured from the expected value is experimentally studied. A correction function instead of a simple exponential function is used to fit the experiment data. The validation of the correction function is checked using the experimental data of several test samples: YAP, NaI(Tl) and LSO. The results show that the correction function well fits the data and the reasonable fluorescent lifetimes are obtained.

Theoretical and numerical analysis of coherent Smith-Purcell radiation
BEI Hua, DAI Zhi-Min
2008, 32(11): 916-923. doi: 10.1088/1674-1137/32/11/014

Coherent enhancement of Smith-Purcell radiation has attracted people's attention not only in adopting a better source but also in beam diagnostics aspect. In this paper, we study the intrinsic mechanism of coherent Smith-Purcell radiation on the basis of the van den Berg model. The emitted power of Smith-Purcell radiation is determined by the bunch profile in transverse and longitudinal directions. For short bunch whose longitudinal pulse length is comparable with the radiation wavelength, it can be concluded approximately that the power is proportional to the square number of electrons per bunch.

Optimal sorting method and application to SSRF booster dipoles
ZHANG Man-Zhou, HOU Jie, LI Hao-Hu, LIU Gui-Min, LI De-Ming
2008, 32(11): 924-927. doi: 10.1088/1674-1137/32/11/015

As the dipoles of SSRF booster are powered in series, the magnet field error varies from magnet to magnet and results in bad beam quality. Sorting and installing magnets according to the measured field errors so that the errors on different magnets are partially compensated with each other, has been the easiest way in many cases to reduce the detrimental effects of the errors without introducing complications. Based on the magnet field measurement results, we investigated and implemented the sorting of dipoles using a method mixed by local cancellation and simulated annealing, and it's found to be quite effective.

Study on ILC bunch compressor
ZHU Xiong-Wei, GAO Jie
2008, 32(11): 928-930. doi: 10.1088/1674-1137/32/11/016

In this paper, we have found a new set of parameters for the short two-stage
ILC bunch compressors. The RF sections are both in the accelerating phase rather than the decelerating phase to improve the accelerating efficiency. We have also studied the CSR related issues. The results show that the microbunch instability exists extensively in the second bunch compressor, but the emittance dilution is small due to the relatively long bunch.

Fabrication of the high power input coupler for BEPCⅡ superconducting cavities
HUANG Tong-Ming, MA Qiang, PAN Wei-Min, WANG Guang-Wei
2008, 32(11): 931-933. doi: 10.1088/1674-1137/32/11/017

The BEPCII storage ring adopts two 500 MHz superconducting cavities (SCC). Each one is equipped with a 500 MHz input power coupler. The coupler is to feed 150 kW power in continuous wave (CW) mode with both standing and traveling wave modes. Due to high power feeding and high frequency of the coupler, its fabrication is a big challenge. The fabrication started with two key components,the window and the antenna. Up to now, two sets including windows and antennas have been made by IHEP. And a 270 kW RF power in CW has passed through the coupler during the high power test. The fabrication details are presented in this paper.

Synchrotron radiation,applications of nuclear techniquees,etc
Comparison of two position sensitive gamma-ray detectors based on continuous YAP and pixellated NaI(TI) for nuclear medical imaging applications
ZHU Jie, MA Hong-Guang, MA Wen-Yan, ZENG Hui, WANG Zhao-Min, XU Zi-Zhong
2008, 32(11): 934-938. doi: 10.1088/1674-1137/32/11/018

Dedicated position sensitive gamma-ray detectors based on position sensitive photomultiplier tubes (PSPMTs) coupled to scintillation crystals, have been used for the construction of compact gamma-ray imaging systems, suitable for nuclear medical imaging applications such as small animal imaging and single organ imaging and scintimammography. In this work, the performance of two gamma-ray detectors:a continuous YAP scintillation crystal coupled to a Hamamastu R2486 PSPMT and a pixellated NaI(TI) scintillation array crystal coupled to the same PSPMT, is compared. The results show that the gamma-ray detector based on a pixellated NaI(TI) scintillation array crystal is a promising candidate for nuclear medical imaging applications, since their performance in terms of position linearity, spatial resolution and effective field of view (FOV) is superior than that of the gamma-ray detector based on a continuous YAP scintillation crystal. However, a better photodetector (Hamamatau H8500 Flat Panel PMT, for example) coupled to the continuous crystal is also likely a good selection for nuclear medicine imaging applications.