2008 Vol. 32, No. 10

Measuring D0-D0 mixing in D→f0(980) K* and more
2008, 32(10): 773-775. doi: 10.1088/1674-1137/32/10/001

We investigate the D0-D0 mixing through the doubly Cabibbo suppressed (DCS) channel D0→f0(980)K*0 and its charge conjugate channel, in which the K*0 meson is reconstructed in both K+π and K0 final state. Although the decay D0→f0(980)K* has a small branching ratio, the final state mesons are relatively easy to identify. The f0(980) meson can be replaced by the S-wave π+π state, or a longitudinally polarized vector meson ρ0. All mixing parameters, including the mass difference and decay width difference, can be extracted by studying the time-dependent decay width of these channels. We show that the method is valid in all regions for mixing parameters and it does not depend on the strong phase difference.

Particle and field theory
Significance of absolute energy scale for physics at BESⅢ
FU Cheng-Dong, MO Xiao-Hu
2008, 32(10): 776-780. doi: 10.1088/1674-1137/32/10/002

The effects of absolute energy calibration on BESⅢ physics are discussed in detail, which mainly involve the effects on τ mass measurement, cross section scan measurement, and generic error determination in other measurements.

Study of pure annihilation decays Bd,s→D0D0
LI Ying, HUA Juan
2008, 32(10): 781-787. doi: 10.1088/1674-1137/32/10/003

Within the heavy quark limit and the hierarchy approximation λQCD<< mD<B, we analyze the B→D0D0 and Bs→D0D0 decays, which occur purely via annihilation type diagrams. As a rough estimate, we calculate their branching ratios and CP asymmetries in the perturbative QCD (PQCD) approach. The branching ratio of B→D0D0 is about 3.8×10-5 that is just below the latest experimental upper limit. The branching ratio of Bs→D0D0 is about 6.8×10-4, which could be measured in LHC-b. From the calculation, it is found that this branching ratio is not sensitive to the weak phase angle γ. In these two decay modes, there exist CP asymmetries because of the interference between weak and strong interaction. However, these asymmetries are too small to be measured easily.

Improved Faddeev-Jackiw quantization of the electromagnetic field and Lagrange multiplier fields
YANG Jin-Long, HUANG Yong-Chang
2008, 32(10): 788-792. doi: 10.1088/1674-1137/32/10/004

We use the improved Faddeev-Jackiw quantization method to quantize the electromagnetic field and its Lagrange multiplier fields. The method's comparison with the usual Faddeev-Jackiw method and the Dirac method is given. We show that this method is equivalent to the Dirac method and also retains all the merits of the usual Faddeev-Jackiw method. Moreover, it is simpler than the usual one if one needs to obtain new secondary constraints. Therefore, the improved Faddeev-Jackiw method is essential. Meanwhile, we find the new meaning of the Lagrange multipliers and explain the Faddeev-Jackiw generalized brackets concerning the Lagrange multipliers.

Study of ψ(4415) in the QPC model
ZHAO Shu-Min, LIU Li-Quan, HA Jing, LI Xia, GUO Qing-Lin
2008, 32(10): 793-796. doi: 10.1088/1674-1137/32/10/005

Some authors consider the ψ(4415) to be the 4S or 5S excited tate of a cc pair. Starting from this assumption, we study he decays of the ψ(4415) to DD, D*D*, DSDS, DS*DS*, and get the corresponding branching ratios in terms of the Quark-Pair-Creation (QPC) model. Compared with the experimental data, we find that the results of 4S state agree much better than those of the 5S state. Therefore, it is more reasonable to assume the ψ(4415) to be a 4S state.

Is Ds(2700) a charmed tetraquark state?
WANG Zhi-Gang
2008, 32(10): 797-802. doi: 10.1088/1674-1137/32/10/006

In this article, we assume that the Ds(2700) is a tetraquark state, which consists of a scalar diquark and a vector antidiquark, and calculate its mass with the QCD sum rules. The numerical result indicates that the mass of the vector charmed tetraquark state is about MV=(3.75±0.18) GeV or MV=(3.71±0.15) GeV from different sum rules, which is about 1 GeV larger than the experimental data. Such tetraquark omponent should be very small in the Ds(2700).

Klein-Gordon oscillators in noncommutative phase space
WANG Jian-Hua, LI Kang, Dulat Sayipjamal
2008, 32(10): 803-806. doi: 10.1088/1674-1137/32/10/007

We study the Klein-Gordon oscillators in non-commutative (NC) phase space. We find that the Klein-Gordon oscillators in NC space and NC phase-space have a similar behaviour to the dynamics of a particle in commutative space moving in a uniform magnetic field. By solving the Klein-Gordon equation in NC phase space, we obtain the energy levels of the Klein-Gordon oscillators, where the additional terms related to the space-space and momentum-momentum non-commutativity are given explicitly.

particle and nuclear astrophysics and cosmology
Estimation of the proton energy spectrum in knee region by analog read-out ofARGO-YBJ experiment
QU Xiao-Bo, CHEN Song-Zhan, ZHA Min, ZHANG Xue-Yao, FENG Cun-Feng
2008, 32(10): 807-811. doi: 10.1088/1674-1137/32/10/008

Based on the six months data set of ARGO-YBJ experiment with analog read-out and its Monte Carlo simulation, we study the difference between different primaries induced showers by using the space-time information of the charged particles in Extensive Air Showers. With five parameters which can efficiently pick out primary proton induced showers as inputs of an artificial neural network, the proton spectrum from 100 TeV to 10 PeV can be obtained.

Nuclear and ion Physics
Double folding model calculation applied to fusion reactions
ZHANG Gao-Long, LE Xiao-Yun
2008, 32(10): 812-815. doi: 10.1088/1674-1137/32/10/009

The interaction potential between a spherical and a deformed nucleus is calculated within the double-folding model for deformed nuclei. We solve the double folding potential numerically by using the truncated multipole expansion method. The shape, separation and orientation dependence of the interaction potential, fusion cross section and barrier distribution of the system 16O+154Sm are investigated by considering the quadrupole and hexadecapole deformations of 154Sm. It is shown that the height and the position of the barrier depend strongly on the deformation and the orientation angles of the deformed nucleus. These are quite important quantities for heavy-ion fusion reactions, and hence produce great effects on the fusion cross section and barrier distribution.

Langevin study of neutron emission in the reactions 16O+181Ta and 19F+178Hf
YE Wei, WU Feng, YANG Hong-Wei
2008, 32(10): 816-819. doi: 10.1088/1674-1137/32/10/010

The pre-scission neutrons measured in the reactions 16O+181Ta and 19F+178Hf are studied via a Langevin equation coupled with a statistical decay model. We find that because of the mass asymmetry of different entrance channels, the spin distributions of compound nuclei would be different, consequently, the measured neutrons in these two reactions would also different. This means that the entrance channel will affect the particle emission in the fission process of hot nuclei.

Detection Technology and Methods
Thermal experiment of silicon PIN detector
CHEN Hong-Fei, ZOU Ji-Qing, SHI Wei-Hong, ZOU Hong, HU Ran-Sheng, TIAN Da-Yu
2008, 32(10): 820-824. doi: 10.1088/1674-1137/32/10/011

The experiment of this paper is the thermal test of the leakage current of silicon PIN detector. Raising temperature may cause the detector to increase leakage current, decrease depletion and increase noise. Three samples are used in the experiment. One (called ΔE) is the sample of 100 μm in thickness. The other two (called E1 and E2) are stacks of five detectors of 1000 μm in thickness. All of them are 12 mm in diameter. The experiment has been done for 21 hours and with power on continuously. The samples have undergone more than 60℃ for about one hour. They are not degenerated when back to the room temperature. The depletion rate is temperature and bias voltage related. With the circuit of the experiment and temperature at 35℃, ΔE is still depleted while E1 and E2 are 94.9% and 99.7% depleted respectively. The noises of the samples can be derived from the values at room temperature and the thermal dependence of the leakage currents. With the addition of the noise of the pre-amplifier, the noises of E1, E2 and ΔE at 24℃ are 16.4, 16.3, and 10.5 keV (FWHM) respectively while at 35℃ are about 33.6, 33.1, and 20.6 keV (FWHM) respectively.

Study of readout and cross-talks for multi-strip RPC with PSpice simulation
WANG Ya-Ping, HE Xiao-Chun, CAI Xu
2008, 32(10): 825-830. doi: 10.1088/1674-1137/32/10/012

An electrical model for multi-strip resistive plate chamber (RPC) is presented, and a comparison between simulation results and test data is carried on. Based on the model, the influences of the RPC's design parameters on the readout are studied with PSpice simulation. Cross-talk (CT) phenomenon is observed and the relative amplitudes of the CT are studied for different design parameters.

Fast simulation of the forward tracking detector of HPLUS
ZHANG Ya-Peng, YAO Nan, XIAO Zhi-Gang, ZHENG Chuan, XU Hu-Shan, JIN Gen-Ming, FAN Rui-Rui, FU Fen, YUE Ke, LIANG Jin-Jie, CHEN Ruo-Fu, SUN Zhi-Yu, DUAN Li-Min, YUAN Xiao-Hua, XU Hua-Gen
2008, 32(10): 831-836. doi: 10.1088/1674-1137/32/10/013
The necessity of installing a forward tracking detector stack is discussed for the Hadron Physics LanzhoU Spectrometer(HPLUS). A local tracker is developed to solve the multi-track finding problem. The track candidates are searched iteratively via Hough Transform. The fake tracks are removed by a least square fitting process. With this tracker we have studied the feasibility of
pp→pp+φ(→K+K), a typical physical channel proposed on HPLUS. The single track momentum resolution due to the uncertainty of the positioning in FTD is 1.3%. The multiple scattering effect contributes about 20% to the momentum resolution in the FTD coverage. The width and the signal-to-background ratio of the reconstructed φ are 1.51 MeV and 4.36, respectively, taking into account the direct Kaon channel pp→pp+K+K as background. The geometry coverage of FTD for φ events is about 85.4%. Based on the current fast simulation and estimation, the geometrical configuration of FTD meets the physical requirement of HPLUS under the current luminosity and multiplicity conditions. The tracker is applicable in the full simulation coming next and is extendable to other tracking component of HPLUS.
RF deflecting cavity design for bunch length measurement of photoinjector at Tsinghua University
SHI Jia-Ru, CHEN Huai-Bi, TANG Chuan-Xiang, HUANG Wen-Hui, DU Ying-Chao, ZHENG Shu-Xin, REN Li
2008, 32(10): 837-841. doi: 10.1088/1674-1137/32/10/014

RF deflecting cavity can be used for bunch length measurement and is designed to diagnose the beam produced by the photocathode electron gun which was built at Tsinghua University for the Thomson scattering experiment. Detailed discussion and calculation for measuring the 3.5 MeV bunch and another with further acceleration to 50 MeV, which is under development, are presented. A standing-wave deflecting cavity working at 2856 MHz is designed and the power feeding system has been planned.

Axial electric wake field inside the induction gap exited by the intense electron beam
ZHANG Kai-Zhi, ZHANG Huang, LONG Ji-Dong, YANG Guo-Jun, HE Xiao-Zhong, WANG Hua-Cen
2008, 32(10): 842-845. doi: 10.1088/1674-1137/32/10/015

While an intense electron beam passes through the accelerating gaps of a linear induction accelerator, a strong wake field will be excited. In this paper a relatively simple model is established based on the interaction between the transverse magnetic wake field and the electron beam, and the numerical calculation in succession generates a magnetic wake field distribution along the accelerator and along the beam pulse as well. The axial electric wake field is derived based on the relation between field components of a resonant mode. According to some principles in existence, the influence of this field on the high voltage properties of the induction gap is analyzed. The Dragon-I accelerator is taken as an example, and its maximum electric wake field is about 17 kV/cm, which means the effect of the wake field is noticeable.

Study of multipacting effect in superconducting cavity
ZHANG Meng, ZHAO Ming-Hua
2008, 32(10): 846-848. doi: 10.1088/1674-1137/32/10/016

A number of superconducting cavities of axis-symmetric geometry have been considered to study the effect in order to achieve the desired performance. It is shown that the multipacting effect is strongly dependent on the condition of the RF surface and can be suppressed with reconsideration of the geometry. The simulation result is compared with the result of the semi-analytical model in the end.

Preliminary study of residual orbit oscillation in BEPCⅡ
MA Hui-Zhou, XU Gang, LEI Ge, CAO Jian-She, MA Li, ZHANG Lei, YUE Jun-Hui, SUI Yan-Feng
2008, 32(10): 849-851. doi: 10.1088/1674-1137/32/10/017

BEPCII has two rings each with an injection system. The injection system of each ring consists of two kicker magnets and a septum magnet. The injection layout of two rings is the same. Both two kickers would kick the beam in horizontal plane. The betatron phase advance in the horizontal plane between two kickers is designed exactly 180° in order to reduce the perturbation to the circulating beams during injection. In fact, the residual orbit oscillation will originate because of the existence of a variety of errors. The Librea Electron BPM processor is used to acquire the beam position data in turn-by-turn mode and to analyze the residual orbit oscillation. According to the measurement results, minimization of the residual orbit oscillation can be done by adjusting the peak field strength and trigger timing delay of two kickers. With very small residual orbit oscillation the two beams can keep collision condition during the injection.

Synchrotron radiation,applications of nuclear techniquees,etc
A non-IQ sampling controller in low level RF system
YIN Cheng-Ke, DAI Zhi-Min, LIU Jian-Fei, ZHAO Yu-Bin, ZHANG Tong-Xuan, FU Ze-Chuan, LIU Wei-Qing
2008, 32(10): 852-856. doi: 10.1088/1674-1137/32/10/018

This paper describes a non-IQ controller for digital Low Level RF (LLRF) feedback control. Based on this non-IQ sampling method, arbitrary frequency relationship between ADC/DAC sampling clocks and IF signals can be employed. The nonlinearity in digital conversion can be reduced and the system dynamic performance improved. This paper analyzes the nonlinearity in conventional IQ sampling, gives the state variable description of the non-IQ algorithm, presents an implementation and its synchronization, and compares its performances with IQ sampling.