2009 Vol. 33, No. 01

Particle and field theory
A possible signature of new physics at BES-Ⅲ
LI Hai-Bo, ZHANG Xue-Yao
2009, 33(01): 1-5. doi: 10.1088/1674-1137/33/1/001
Abstract:

The recent observations of the purely leptonic decay Ds+→μ+νμ and τ+ντ at CLEO-c and B factory may allow a possible contribution from a charged Higgs boson. One such measurement of the decay constant fDs differs from the most precise unquenched lattice QCD calculation by a level of 4σ. Meanwhile, the measured ratio, BR (Ds+→μ+νμ/BR(D+→μ+νμ), is larger than the standard model prediction at a 2.0σ level. We discuss that the precise measurement of the ratio BR (Ds+→μ+νμ/BR(D+→μ+νμ) at BES-Ⅲ will shed light on the presence of new intermediate particles by comparing the data with the theoretical predictions, especially, the predictions of high precise unquenched lattice QCD calculations.

Top pair production in the littlest Higgs model with T-parity
ZHAO Guo-Ming, LI Yong-Sheng, WANG Li-Na
2009, 33(01): 6-9. doi: 10.1088/1674-1137/33/1/002
Abstract:

In the framework of the littlest Higgs model with T-parity, we study the top pair production at the next generation colliders like LHC and ILC. We find that the order O(αs) corrections to the standard model top pair production cross section at LHC can be very small and the magnitude is below 1%. However, the magnitude of corrections to the standard model top pair production rate at ILC
may be over 5% for reasonable values of the parameters. Besides this, the corrections to the asymmetry ALR(tt) may be more sizable. Therefore, the top pair production at ILC may serve as a probe of the littlest Higgs model with T-parity, especially the asymmetry ALR(tt).

Quantum electrodynamics with arbitrary charge on a noncommutative space
CAI Shao-Hong, LONG Zheng-Wen
2009, 33(01): 10-14. doi: 10.1088/1674-1137/33/1/003
Abstract:

Using the Seiberg-Witten map, we obtain a quantum electrodynamics on a
noncommutative space, which has arbitrary charge and keep the gauge
invariance to at the leading order in theta. The one-loop divergence and
Compton scattering are reinvestigated. The noncommutative effects are larger
than those in ordinary noncommutative quantum electrodynamics.

particle and nuclear astrophysics and cosmology
The competition of neutrino energy loss due to the pair, photo-, plasma process at the late stages of stellar evolution
LIU Jing-Jing
2009, 33(01): 15-19. doi: 10.1088/1674-1137/33/1/004
Abstract:

Based on the Weinberg-Salam theory, the competition of the Neutrino Energy Loss (NEL) rates due to the pair, photo- and plasma process are canvassed. The ratio factor C1, C2 and C3 which correspond the different contributions of the pair, photo- and plasma neutrino process to those of the total NEL rates are accurately taken into account. The ratio factors are very sensitive to the temperature and density. The ratio factor C2 always is lower than the ratio factor C1 and C3. The pair NEL process is the dominant contribution before the
crossed point O(C1 =C3=0.45) and the plasma NEL process will be the main dominant contribution after the crossed point O. With increasing temperature, the crossed point $O$ will move to the direction of higher density.

Nuclear and ion Physics
Luminosity determination for the dd→α K+K experiment at ANKE/COSY
Dzyuba Alexey, Büscher Markus, (for the ANKE Collaboration)
2009, 33(01): 20-23. doi: 10.1088/1674-1137/33/1/005
Abstract:

High resolution studies of a0/f0(980) decays into channels involving open strangeness are currently being performed at COSY-J\"ulich. As a "filter'' for isospin-zero intermediate states, {i.e.} to selectively produce the f0(980) resonance, the $\rm dd\to \upalpha K+K reaction was measured with the magnetic ANKE spectrometer. In order to determine the luminosity of this experiment, the elastically and quasi-elastically scattered deuterons were recorded simultaneously with the αK+Kevents. Here we report about the luminosity determination via investigating the (quasi-) elastic deuterons at ANKE.

Least square fitting of low resolution gamma ray spectra with cubic B-spline basis functions
LIU Liang-Gang, QI Dong-Xu, YOU Zhong, XU Ao-Ao
2009, 33(01): 24-30. doi: 10.1088/1674-1137/33/1/006
Abstract:

In this paper, the least square fitting method with the cubic B-spline basis functions is derived to reduce the influence of statistical fluctuations in the gamma ray spectra. The derived procedure is simple and automatic. The results show that this method is better than the convolution method with a sufficient
reduction of statistical fluctuation.

Theoretical calculation of kerma coefficients for n+16O reaction below 30 MeV
LIU Ji-Feng, SUN Xiao-Jun
2009, 33(01): 31-35. doi: 10.1088/1674-1137/33/1/007
Abstract:

On the basis of the light nuclear reaction model, a new kerma coefficient formula has been developed. In terms of the analysis for n+16O reactions below 30 MeV, the average energies of all kinds of the emitted particles are presented. The calculated partial kerma coefficients agree well with the existing experimental data. The discrepancies of the total kerma coefficients between the calculation and the measurement are analyzed in detail.

Trace initial interaction from final state observable in relativistic heavy ion collisions
LIU Lian-Shou, WU Yuan-Fang
2009, 33(01): 36-41. doi: 10.1088/1674-1137/33/1/008
Abstract:

In order to trace azimuthal angle dependence of the initial interaction in ultra-relativistic heavy ion collision, two azimuthal multiplicity-correlation patterns
— neighboring and fixed-to-arbitrary angular-bin correlation patterns — are suggested. From the simulation of Au + Au collisions at √SNN=200 GeV by using the Monte Carlo models RQMD with hadron re-scattering and AMPT with and without string melting, we observe that the correlation patterns change
gradually from out-of-plane preferential one to in-plane preferential one when the centrality of collision shifts from the central collision to peripheral collision, meanwhile the anisotropic collective flow v2 keeps positive in all cases. This regularity is found to be collision energy independent. The physics behind the
two opposite trends of correlation patterns, in particular, the presence of out-of-plane correlation patterns at RHIC energy, are discussed.

Detection Technology and Methods
Monte Carlo studies of micromegas as a neutron detector and its track reconstruction
ZHANG Xiao-Dong, WANG Wen-Xin, YANG He-Run, YANG Zheng-Cai, HU Bi-Tao
2009, 33(01): 42-46. doi: 10.1088/1674-1137/33/1/009
Abstract:

In this paper a two dimensional readout micromegas detector with a polyethylene foil as converter was simulated on GEANT4 toolkit and GARFIELD for fast neutron detection. A new track reconstruction method based on time coincidence technology was developed in the simulation to obtain the incident neutron position. The results showed that with this reconstruction method higher spatial resolution was achieved.

ELDRS and dose-rate dependence of vertical NPN transistor
LU Wu, REN Di-Yuan, WANG Gai-Li, YU Xue-Feng, GUO Qi
2009, 33(01): 47-49. doi: 10.1088/1674-1137/33/1/010
Abstract:

The enhanced low-dose-rate sensitivity (ELDRS) and dose-rate dependence of vertical NPN transistors are investigated in this article. The results show that the vertical NPN transistors exhibit more degradation at low dose rate, and that this degradation is attributed to the increase on base current. The oxide trapped positive charge near the SiO2-Si interface and interface traps at the interface can contribute to the increase on base current and the two-stage hydrogen mechanism associated with space charge effect can well explain the experimental results.

New test and analysis of position-sensitive-silicon-detector
GE Yu-Cheng, WANG He, FAN Feng-Ying, QIAO Rui, LU Fei, SONG Yu-Shou, YE Yan-Lin
2009, 33(01): 50-53. doi: 10.1088/1674-1137/33/1/011
Abstract:

We have tested and analyzed the properties of two-dimensional Position-Sensitive-silicon-Detector (PSD) with new integrated preamplifiers. The test demonstrates that the best position resolution for 5.5 MeV α particles is 1.7 mm (FWHM), and the best energy resolution is 2.1%, which are notably better than the previously reported results. A scaling formula is introduced to make the absolute position calibration.

Simulation of a modified neutron detector applied in CSNS
WANG Qing-Bin, WU Qing-Biao
2009, 33(01): 54-57. doi: 10.1088/1674-1137/33/1/012
Abstract:

We simulate the response of a modified Anderson-Braun rem counter in the energy range from thermal energy to about 10 GeV using the FLUKA code. Also, we simulate the lethargy spectrum of CSNS outside the beam dump.
Traditional BF3 tube is replaced by the 3He tube, a layer of 0.6 cm lead is added outside the boron doped plastic attenuator and a sphere configuration is adopted. The simulation result shows that its response is exactly fit to H*(10) in the neutron energies between 10 keV and approximately 1 GeV, although the monitor slightly underestimates H*(10) in the energy range from thermal energy to about 10 keV. According to the characteristics of the CSNS, this modified counter increases the neutron energy response by 30% compared with the traditional monitors, and it can be applied in other kinds of stray field rich of high energy neutrons.

Accelerator
Investigation of a method to calculate spontaneous radiation spectrafrom relativistic electrons in undulators
HE Jian-Hua
2009, 33(01): 58-64. doi: 10.1088/1674-1137/33/1/013
Abstract:

Undulators are key devices to produce brilliant synchrotron radiation at the synchrotron radiation facilities. In this paper we present a numerical computing method, including the computing program that has been developed to calculate the spontaneous radiation emitted from relativistic electrons in undulators by simulating the electrons' trajectory. The effects of electron beam emittance and energy spread have also been taken into account. Comparing with other computing methods available at present, this method has a few advantages with respect to several aspects. It can adopt any measured or arbitrarily simulated 3D magnetic field and arbitrary electron beam pattern for the calculation and it's able to analyze undulators of any type of magnetic structure. It's expected to predict precisely the practical radiation spectrum. The
calculation results of a short period in-vacuum undulator and an Elliptically Polarized Undulator (EPU) at Shanghai Synchrotron Radiation Facility (SSRF) are presented as examples.

Improved nonlinear optimization in the storage ring of the modernsynchrotron radiation light source
LIU Gui-Min, HOU Jie, CHEN Guang-Ling, CHEN Sen-Yu
2009, 33(01): 65-73. doi: 10.1088/1674-1137/33/1/014
Abstract:

In the storage ring of the third generation light sources, nonlinear optimization is an indispensable course in order to obtain ample dynamic acceptances and to reach high injection efficiency and long beam lifetime, especially in a low emittance lattice. An improved optimization algorithm based on the single resonance approach, which takes relative weight and initial Harmonic Sextupole Integral Strength (HSIS) as search variables, is discussed in this paper. Applications of the improved method in several test lattices are presented. Detailed analysis of the storage ring of the Shanghai Synchrotron Radiation Facility (SSRF) is particularly emphasized. Furthermore, cancellation of the driving terms is investigated to reveal the physical mechanism of the harmonic sextupole compensation. Sensitivity to the weight and the initial HSIS as well as dependence of the optimum solution on the convergent factor is analyzed.

Study on the RF performance of 2-cell superconducting cavity
LU Xiang-Yang, WANG Er-Dong, ZHAO Kui
2009, 33(01): 74-76. doi: 10.1088/1674-1137/33/1/015
Abstract:

The physical design of the 2-cell superconducting cavity is presented. The RF parameters of the cavity and HOMs (high order modes) are reported. In this paper, we put the emphasis on the analysis of the HOMs and interaction between beam and cavity.

Development of a China test cryomodule for ILC
ZHAI Ji-Yuan, LI Chun-Hua, SUN Yi, HOU Zhi-Long, GAO Jie, ZHAO Tong-Xian, LU Wen-Hai, ZONG Zhan-Guo, LIU Li-Qiang, ZHANG Liang
2009, 33(01): 77-80. doi: 10.1088/1674-1137/33/1/016
Abstract:

Research and development of a 1.3 GHz 9-cell cavity test cryomodule were carried out by a collaboration group between IHEP (Institute of High Energy Physics) and TIPC (Technical Institute of Physics and Chemistry) in China. The cryomodule is a "test model" for the ILC cryomodule, and a key component of a superconducting accelerator test unit which will be built in the near future, also can be used as a horizontal test facility for 1.3~GHz 9-cell cavities. This paper presents the development status of the cryomodule, including structure design, cryogenic flow diagram, thermal and mechanical simulations, heat load estimation and etc.

Synchrotron radiation,applications of nuclear techniquees,etc
Positronium annihilation in silica aerogel studied by a positron age-momentum correlation technique
ZHANG Lan-Zhi, WANG Bao-Yi, YU Run-Sheng, ZHANG Zhi-Ming, LI Dao-Wu, WEI Long
2009, 33(01): 81-84. doi: 10.1088/1674-1137/33/1/017
Abstract:

A high-performance positron age-momentum correlation (AMOC) spectrometer was newly developed. The counting rate is increased up to 200 cps much larger than the value 20~cps reported by other international groups. And at the same time, the time resolution still keeps at the international level of 220 ps. Furthermore, positronium (Ps) annihilation in silica aerogel was investigated by AMOC, which indicates: (1) Ps annihilation between the grains dominantly undergoes pick-off process and spin conversion from o-Ps to p-Ps; (2) Annealing below 400 ℃ changes the grain surface conditions, i. e. the desorption of hydrogen and the decrease of the defect centers concentration.