Data Offline Calibration for the BES-Ⅱ TOF System

Data offline calibration and reconstruction for the BES-Ⅱ TOF system are reported in this paper. After applying calibration constants to correct the measured raw data, a the resolution of 180 ps is obtained for the new TOF system. The power of charged particle identification is improved. The momentum for the 3σπ/K separation goes up to 0.93 GeV/c.     

Muon Identification Using the Efficiencies Ratio Method at BESⅡ

The momentum and polar angle depended position resolution and hit efficiency in each layer of BES(Ⅱ) muon detector are calibrated by using cosmic ray and hadron samples. Based on the calibration results, the efficiencies ratio function is constructed to separate μ/π effectively and applied in physics analysis.     

Calibration of RPC-based muon detector at BESⅢ

The calibration algorithm for RPC-based muon detector at BESIII has been developed. The calibration method, calibration error and algorithm performance are studied. The primary results of efficiency and noise at layer, module and strip levels have been calibrated with cosmic ray data. The calibration constants are available for simulation and reconstruction tuning. The results of Monte Carlo and data are also compared to check the validation and reliability of the algorithm.     

Calibration of RPC-based muon detector at BESⅢ

The calibration algorithm for RPC-based muon detector at BESⅢ has been developed. The calibration method, calibration error and algorithm performance are studied. The primary results of efficiency and noise at layer, module and strip levels have been calibrated with cosmic ray data. The calibration constants are available for simulation and reconstruction tuning. The results of Monte Carlo and data are also compared to check the validation and reliability of the algorithm.     

Calibration study of the X-T relation for the BESⅢ drift chamber

Offline calibration plays an important role in BESⅢ offline data processing. In order to achieve good spatial and momentum resolution, it is necessary to implement high precision offline calibration for the BESⅢ drift chamber. This paper studies the time-to-distance relations, which are important calibration constants for track reconstruction. The parameterization of the time-to-distance relation, studies of left-right asymmetry and studies of variation with entrance angle are performed. The impact of dead channels on the time-to-distance relation is given special attention in order to reduce the shift in measured momentum for tracks passing near dead cells. Finally we present the resolutions for barrel Bhabha events (|cosθ|<0.8) from a J/ψ data set taken in 2012. The average spatial resolution is 123 μ and the momentum resolution for 1.548 GeV/c Bhabha tracks is 11.9 MeV/c.     

Calibration study of the X-T relation for the BESⅢ drift chamber

Offline calibration plays an important role in BES offline data processing. In order to achieve good spatial and momentum resolution, it is necessary to implement high precision offline calibration for the BES drift chamber. This paper studies the time-to-distance relations, which are important calibration constants for track reconstruction. The parameterization of the time-to-distance relation, studies of left-right asymmetry and studies of variation with entrance angle are performed. The impact of dead channels on the time-to-distance relation is given special attention in order to reduce the shift in measured momentum for tracks passing near dead cells. Finally we present the resolutions for barrel Bhabha events(|cos θ|< 0.8) from a J/ψ data set taken in 2012. The average spatial resolution is 123 μm and the momentum resolution for 1.548 Ge V/c Bhabha tracks is 11.9 Me V/c.     

Analysis of the Factors that Influence the Time Resolution of TOF in BESⅢ Detector

In TOF measurement, the factors that can increase the time resolution include noise, amplitude measurement error, and the difference of pulse amplitudes and shapes. This article discusses how these factors affect time resolution, and performs quantitative analysis based on the GEANT4 simulation result of the BESⅢ's TOF detector. The result shows that the discriminator level must be selected carefully. To get better time resolution, pulse waveform digitizing is necessary.     

Study of Neutral Track Measurement at BESⅡ

The measurement errors of the deposited energy and position of neutral tracks in Barrel Shower Counter (BSC) of BESⅡ are investigated. The errors of energy and position of real data are determined by radiative Bhabha events, while the errors of Monte Carlo Data are determined by e⁺e^－→γγ events. Then the corrections are tested by the selected ρπ sample, which shows better pull and Confidence Level distribution after the correction. The results are already applied to the kinematic fitting, which can improve the physics results at BESⅡ.     

BESⅡ顶点探测器

介绍了BESⅡ上正在运行的顶点探测器基本结构、特点和性能(覆盖95%×4π立体角,空间分辨σ_rφ≈100μm,σ_z≈2mm),及工作方式和电子学读出,并进一步介绍它在北京谱仪上的作用.     

Study of the p and p Identification at BES Ⅱ

Based on three methods of particle identification (PID) of BES,we study the identification of p and p in momentum range from 0.3 to 1.2 GeV using real particle samples of e,μ,π,K,p and p which were collected in 2-5GeV R scan,J/(ψ) and ψ′ data taking periods. The paper presents the optimized method of PID:p(p) is identified by dE/dx only if momentum below 0.6GeV,and by TOF or the combination of dE/dx and TOF for higher momentum.The PID efficiency of p, p and contamination from the other charged particles are also given.     

Development of Silicon Multi-strip Detector

Position sensitive detector is very important for nuclear physics experiment. There several techniques can be used to fabricate position sensitive detector, for example, Si-surface barrier method, diffusion method, ion implantation and planar process etc. Among all the techniques mentioned above planar process is the best one. We have developed batch of position sensitive detector -- silicon multi-strip detector by using planar process.     

Simulation System of Internal-target Detector at HIRFL-CSRm

HIRFL-CSRm will accelerate the proton beam up to 2.8 GeV. The interesting physics, such as the hadron spectrum, di-baryon state and the rare decay mode of the neutral mesons can be investigated with such beams. The corresponding detector as introduced in Ref.[1] is an internal-target 4π detector which is composed of the forward detector (including position detector and hadron calorimeter) to detect particles emitted at forward angles, and the center detector (including tracker, plastic scintillator barrel and EM calorimeter) to measure momentum and energy loss of the charged particle, and the energy and emission angle of the high energy photon at central and backward angles. To design such a complex detector, the Monte-Carlo (MC) simulation is definitely necessary.     

BESⅡ上光子探测效率的研究

利用J/ψ→ρπ衰变道,对BESⅡ上BSC对于光子的探测效率做了细致的研究.结果表明在从探测器光子能量阈值直到BES上可产生的最大光子能量范围内,用目前的Monte Carlo可以在1%—3%的精度下模拟光子的探测效率.并且对Monte Carlo在探测效率上与数据的差别进行了详细研究.同时用质心系能量s=3.770GeV处的e+e–→γe+e–数据检验了高能区MonteCarlo和数据的探测效率都达到100%,并且在1%精度下是一致的     

Multi-Variable Particle ID for BESⅡ Physics Analysis

A multi-variable particle identification method is developed for the BESⅡ physics analysis. Besides the traditionally used TOF-T and dE/dx information, TOF-Q and BSC-E are also used to improve the particle discrimination ability. It is shown that the particle identification efficiency, misidentification probability and systematic error could be improved with this new method. The multi-variable method can be extended to even more variables, and can be used in other experiments.     

Future Physics Programme of BESⅢ

There has recently been a dramatic renewal of interest in hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like XYZ states at BESⅢ and B factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related X(1835) meson state at BESⅢ, as well as the threshold measurements of charm mesons and charm baryons. We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESⅢ during the remaining operation period of BEPCⅡ. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCⅡ to higher luminosity.     

Muon–hadron detector of the carpet-2 array

The 1-GeV muon–hadron detector of the Carpet-2 multipurpose shower array at the Baksan Neutrino Observatory, Institute for Nuclear Research, Russian Academy of Sciences (INR, Moscow, Russia) is able to record simultaneously muons and hadrons. The procedure developed for this device makes it possible to separate the muon and hadron components to a high degree of precision. The spatial and energy features of the muon and hadron extensive-air-shower components are presented. Experimental data from the Carpet-2 array are contrasted against data from the EAS-TOP and KASCADE arrays and against the results of the calculations based on the CORSIKA (GHEISHA + QGSJET01) code package and performed for primary protons and iron nuclei.     

Study of Kso Reconstruction and Lifetime Measurement at BESⅡ

The beam collision center of the BEPC has slightly shifted from geometrical origin of the BES detector and the beam bunch of the BEPC also has certain size. For these reasons, to measure K_s^o lifetime, primary vertex reconstruction must be carried out. After the investigation of di-muon, bhabha and hadron events, the beam collision center for each run is determined by bhabha and di-muon events. For the large branching ratio of and the existence of the resonance of KⅡ0 , this channel is chosen to provide much pure K_s^o signal. With the aid of M. C. tools at BES Ⅱ , existing software for secondary vertex reconstruction is adjusted and improved. A new method of secondary vertex determination is used and a better position resolution of secondary vertex is obtained. The lifetime of Ks0 is measured with channel and the inclusive K_s^o mass is investigated with BES Ⅱ 's 50M J/ψ data sample, which give consistent Ks0 lifetime and mass with PDG' s value within error. 1C fit on K⁰_s mass is also studied with M. C. events. The resolution of momentum and energy of 7π+ , π- and K, is improved too.