Coolant choice for the central beryllium pipe of the BESⅢ beam pipe

In order to take away much more heat on the BESⅢ beam pipe to guarantee the normal particle detection,EDM-1（oil No.1 for electric discharge machining）,with good thermal and flow properties was selected as the candidate coolant for the central beryllium pipe of the BESⅢ beam pipe.Its cooling character was studied and dynamic corrosion experiment was undertaken to examine its corrosion on beryllium.The experiment results show that EDM-1 would corrode the beryllium 19.9 μm in the depth in 10 years,which is weak and can be neglected.Finite element simulation and experiment research were taken to check the cooling capacity of EDM-1.The results show that EDM-1 can meet the cooling requirement of the central beryllium pipe.Now EDM-1 is being used to cool the central beryllium pipe of the BESⅢ beam pipe.     

What has been measured by reflection magnetic circular dichroism in Ga1-xMnxAs/GaAs structures？

An explicit expression of reflection magnetic circular dichroism （RMCD） has been derived, taking into account the interference effect that arises from multiple internal reflections in an air/Ga1-xMnxAs/GaAs dielectric layered system. It unambiguously shows that the RMCD signal is composed by three terms. In addition to the conventional term, which is sufficient in the absence of interference, an oscillatory term is required. Both of them are related to the imaginary part εxy of the off-diagonal element of the dielectric tensor. One also becomes aware that in this case RMCD is not actually determined only by the imaginary part εxy of the off-diagonal element of the dielectric tensor, as has been widely accepted. In fact, the real part εxy of the off-diagonal element will substantially mix into the measured RMCD results by another oscillatory cos θ form. It can even reverse the sign of RMCD, when the Gal_xMnxAs layer becomes thicker. The main aspects of these predictions were used to reasonably explain the RMCD results measured in three different types of samples. Our work will bring about a reconsideration of how to correctly explain RMCD results.     

Charmonium results from BES

Using ～ 14 × 10^6 ψ（2S） and ～ 58 × 10^ J/ ψ data collected at BES Ⅱ/BEPC, the branching fraction of ψ（2S）→Ω-Ω^＋ is measured with about 5a statistical significance. The A electric dipole and ∧ decay parameter are studied using the decay J/ψ →∧∧→ ppπ^＋π^-. Using （106±3）× 10^6 ψ（2S） decays collected at BESⅢ/BEPC Ⅱ, we have obtained some interesting physics results. The branching fractions of XcJ→π^0π^0, ηη are measured with precision improved. The mass and width of he（l^1P1） state, together with the branching fractions of Br（ψ（2S） →π^0hc） and Br（hc →γηc） are the first measurements. Surprisingly, the decays of Xc1→φφ, ωω, and ωφ are firstly observed in BESⅢ data.     

Online measurement of the BEPCⅡ background using RadFET dosimeters

To monitor the integral dose deposited in the BESⅢ electromagnetic calorimeter whose performance degrades due to exposure to the BEPC Ⅱ background, a 400 nm IMPL RadFET dosimeter-based integral dose online monitor system is built, After calibration with the ^60Co source and verification with TLD in the pulse radiation fields, an experiment was arranged to measure the BEPC Ⅱ background online. The results are presented.     

Lepton-number-violating decays of singly-charged Higgs bosons in the type-（Ⅰ＋Ⅱ ） seesaw model

The lepton-number-violating decays of singly-charged Higgs bosons H^± are investigated in the minimal type-（ Ⅰ＋Ⅱ ） seesaw model with one SU（2）L Higgs triplet △ and one heavy Majorana neutrino N1 at the TeV scale. We find that the branching ratios B（H^＋ → 1α^＋υ^-） （for α = e,μ,τ） depend not only on the mass and mixing parameters of three light neutrinos υi （for i = 1, 2, 3） but also on those of N1. Assuming that the mass of N1 lies in the range of 200 GeV to 1 TeV, we figure out the generous interference bands for the contributions of υi and N1 to B（H^＋→ 1α^＋υ^-）. We illustrate some salient features of such interference effects by considering three typical mass patterns of υi, and show that the relevant Majorana CP-violating phases can affect the magnitudes of B（H^＋→ 1α^＋υ^-）） in this parameter region.     

Characterization of tetragonal distortion in a thick Al0.2Ga0.8N epilayer with an AIN interlayer by Rutherford backscattering/channeling

An Al0.2Ga0.8N/AlN/Al0.2Ga0.8N heterostructure was grown by metalorganic chemical vapor deposition on a sapphire （0001） substrate with a thick （〉 1 μm） GaN intermediate layer. The Al composition was determined by Rutherford backscattering （RBS）. Using the channeling scan around an off-normal [1213] axis in the （1010） plane of the Al0.2Ga0.8N layer, the tetragonal distortion eT, which is caused by the elastic strain in the epilayer, is investigated. The results show that eT in the high-quality Al0.2Ga0.8N layer is dramatically released by the AIN interlayer from 0.66% to 0.27%.     

Track reconstruction in the BESⅢ muon counter

The reconstruction algorithm for BESⅢ Muon Counter, MucRecAlg, is developed with the objectoriented language C＋＋ in BESⅢ offine software environment. MucRecAlg consists of the following functions：to find track seeds either from extrapolation of tracks in the main drift chamber or from the fired strips in muon counter, to select fired strips associated to the candidate tracks, to fit the candidate tracks with a linear or quadratic function and to calculate other parameters of the tracks for muon identification. Monte Carlo samples are generated to check the performance of the reconstruction package, such as reconstruction effciency, muon remaining rate and pion rejection rate, etc. The preliminary results show that the pion rejection rate is around 3%—4% while the muon remaining rate is better than 90% in 0.4—1.6 GeV/c momentum region, which meets the requirement as shown in the design report.     

Evolutionary genetic optimization of the injector beam dynamics for the ERL test facility at IHEP

The energy recovery linac test facility （ERL-TF）, a compact ERL-FEL （free electron laser） two-purpose machine, has been proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector was designed and preliminarily optimized. In this paper an evolutionary genetic method, non-dominated sorting genetic algorithm II, is applied to optimize the injector beam dynamics, especially in the high-charge operation mode. Study shows that using an incident laser with rms transverse size of 1-1.2 ram, the normalized emittance of the electron beam can be kept below 1 mm.mrad at the end of the injector. This work, together with the previous optimization of the low-charge operation mode by using the iterative scan method, provides guidance and confidence for future construction and commissioning of the ERL-TF injector.     

Full period superconducting section physics design for injector Ⅱ of China-ADS

The China Accelerator Driven Subcritical System （China-ADS） project, which is a strategic plan and aims to design and build an ADS demonstration facility, has been proposed and launched actively in China. Injector Ⅱ as one of the parallel injectors of China-ADS, and is prompted by the Institute of Modern Physics （IMP）. In this paper, a new scheme with full period lattice structure for the SC section is proposed. In the new scheme, there are sixteen periods, with one superconducting solenoid and one superconducting cavity included in each period. All of the elements are contained in four eryomodules. The dreadful influence of the mismatch caused by period structural change can be avoided, and the beam quality is favorable. In addition, this new scheme has certain advantages in reducing the project＇s difficulty and construction risk. The details of the design and beam dynamic simulation for the full period lattice structure are given in this paper.     

Lagrange multiplier method used in BESⅢ

In this paper, the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment. First we introduce the Lagrange multiplier method and implement kinematic constraints. Then we present the performance of the kinematic fitting algorithm. With the kinematic fitting, we can improve the resolution of track parameters and reduce the background.     

BEPCII丝靶束流截面测量系统

To monitor the beam profile at the end of the linac non-destructively, a wire scanner as a new diagnostic instrument was designed, manufactured and installed in 2007. Since then, several measurements have been carried out using this device. This paper describes the whole system of the wire scanner and the testing results.     

Control application of a superconducting magnet power supply based on EPICS

The superconducting quadrupole magnets （SCQs） are powered by 16 power supplies in the inter- action region of the BEPC Ⅱ. The control application of these power supplies must be interlocked with the quench protection system to protect the superconducting magnet and relevant devices. This paper describes the development procedures of this control application using EPICS and the operating result with the quench protection system on-site.     

Trigger efficiencies at BESⅢ

Trigger efficiencies at BESⅢ were determined for both the J/ψ and ψ＇ data taking of 2009. Both dedicated runs and physics datasets are used; efficiencies are presented for Bhabha-scattering events, generic hadronic decay events involving charged tracks, dimuon events and ψ＇→π＋π-J/ψ, J/ψ→ 1＋1- events.The efficiencies are found to lie well above 99% for all relevant physics cases, thus fulfilling the BESⅢ design specifications.     

Primary vertex reconstruction based on the Kalman filter technique at BESⅢ

Primary vertex reconstruction is crucial to estimate the beam profile in collision experiments. We study the principle of an iterative process, called the Kalman filter method, and apply it to primary vertex reconstruction at BESⅢ. A Newton procedure to find the zero point of the distance function＇s gradient is used for primary vertex finding in 3-dimensional space. Results are obtained based on raw data at BESⅢ.     

Study of low momentum track reconstruction for the BESⅢ main drift chamber

In order to overcome the difficulty brought by the circling charged tracks with transverse momentum less than 120 MeV in the BESⅢ Main Drift Chamber （MDC）, a specialized method called TCurlFinder was developed. This tracking method focuses on the charged track reconstruction under 120 MeV and possesses a special mechanism to reject background noise hits. The performance of the package has been carefully checked and tuned by both Monte Carlo data and real data. The study shows that this tracking method could obviously enhance the reconstruction efficiency in the low transverse momentum region, providing physics analysis with more and reliable data.     

Tuning of the cosmic-ray test system of the BESⅢ drift chamber

The BESⅢ drift chamber and its subsystems need a cosmic-ray test after the chamber construction to check the chamber construction quality,testing the joint operation of the whole system and the performance of the chamber.The noise performance,drift time and charge measurements,and the scanning of channels were examined specifically.The preliminary results of the test indicate that the whole system works well.     

Software alignment of the BESⅢ main drift chamber using the Kalman Filter method

Software alignment is quite important for a tracking detector to reach its ultimate position accuracy and momentum resolution. We developed a new alignment algorithm for the BESⅢ Main Drift Chamber using the Kalman Filter method. Two different types of data which are helix tracks and straight tracks are used to test this algorithm, and the results show that the design and implementation is successful.     

BESⅢ track fitting algorithm

A track fitting algorithm based on the Kalman filter method has been developed for BESⅢ of BEPCⅡ. The effects of multiple scattering and energy loss when the charged particles go through the detector, non-uniformity of magnetic field （NUMF） and wire sag, etc., have been carefully handled. This algorithm works well and the performance satisfies the physical requirements tested by the simulation data.     

An improved interpolating element-free Galerkin method for elasticity

Based on the improved interpolating moving least-squares （ⅡMLS） method and the Galerkin weak form, an improved interpolating element-free Galerkin （ⅡEFG） method is presented for two-dimensional elasticity problems in this paper. Compared with the interpolating moving least-squares （IMLS） method presented by Lancaster, the ⅡMLS method uses the nonsingular weight function. The number of unknown coefficients in the trial function of the ⅡMLS method is less than that of the MLS approximation and the shape function of the ⅡMLS method satisfies the property of Kronecker δ function. Thus in the ⅡEFG method, the essential boundary conditions can be applied directly and easily, then the numerical solutions can be obtained with higher precision than those obtained by the interpolating element-free Galerkin （IEFG） method. For the purposes of demonstration, four numerical examples are solved using the ⅡEFG method.     

A new $N^{}$ resonance as a hadronic molecular state

We report our recent work on a hadronic molecule state of the KKN system with I =1/2 and jR = 1/2＋. We assume that the A（1405） resonance and the scalar mesons, f0（980）, ao（980）, are reproduced as quasi-bound states of KN and KK, respectively. Performing non-relativistic three-body calculations with a variational method for this system, we find a quasibound state of the KIlN system around 1910 MeV below the three-body breakup threshold. This state corresponds to a new baryon resonance of N＊ with JP ： 1/2＋. We find also that this resonance has the cluster structure of the two-body bound states keeping their properties as in the isolated two-particle systems. We also briefly discuss another hadronic molecular state composed by two K and one N, which corresponds to a resonance.