Study of BESⅢ MUC offine software with cosmic-ray data

Cosmic-ray data of 90 M events have been collected and used for calibration,alignment as well as detector tuning. A special tracking algorithm for the BESⅢ muon counter is developed and verified with Monte-Carlo simulation and then further confirmed with the cosmic-ray data. The obtained strip resolutions are in good agreement with the design values. A new alignment approach for the BESⅢ muon counter is confirmed with the cosmic-ray data and proposed to be used in future analysis of experimental data.     

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.     

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.     

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.     

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.     

Online data quality monitoring system at BESⅢ

The online Data Quality Monitoring (DQM) tool plays an important role in the data recording process of HEP experiments. The BESⅢ DQM collects data from the online data flow, reconstructs them with offline reconstruction software and automatically analyzes the reconstructed data with user-defined algorithms. The DQM software is a scalable distributed system. The monitored results are gathered and displayed in various formats, which provides the shifter with current run information that can be used to identify problems quickly. This paper gives an overview of the DQM system at BESⅢ.     

An extended segment pattern dictionary for a pattern matching tracking algorithm at BESⅢ

A pattern matching based tracking algorithm, named MdcPatRec, is used for the reconstruction of charged tracks in the drift chamber of the BES detector. This paper addresses the shortage of segment finding in the MdcPatRec algorithm. An extended segment construction scheme and the corresponding pattern dictionary are presented. Evaluation with Monte-Carlo and experimental data show that the new method can achieve higher efficiency for low transverse momentum tra     

Studies of dE/dx measurements with the BESⅢ

The Beijing Spectrometer Ⅲ（BESⅢ）is a general-purpose detector used for the study of τ-charm physics at the Beijing Electron-Positron Collider Ⅱ（BEPC Ⅱ）.This paper presents our studies of the dE/dx measurement in the drift chamber of BESⅢ,which is important for the identification of charged particles.Corrections applied to the dE/dx measurement in data reconstruction are discussed.After our current dE/dx calibration,a resolution of about 6% has been obtained for minimum ionization particles,and a 3σ K/πseparation is obtained for momenta up to 760 MeV/c.These results meet the design goals of the BESⅢ drift chamber.     

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.     

Monte Carlo tuning for the BESⅢ time-of-flight system

Using experimental data, Monte Carlo tuning is implemented for performance parameters associated with the scintillation counters and readout electronics of the BESⅢ time-of-flight(TOF) system, as part of the full simulation model. The implementation of the tuning is described for simulations designed to reproduce the performance of a number of TOF system parameters, including pulse height, hit efficiency, time resolution, dead channels and background. In addition, comparisons with experimental data are presented.     

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.     

Antiproton identification below threshold with the AMS-02 RICH detector

The Alpha Magnetic Spectrometer(AMS-02),which is installed on the International Space Station(ISS),has been collecting data successfully since May 2011.The main goals of AMS-02 are the search for cosmic anti-matter,dark matter and the precise measurement of the relative abundance of elements and isotopes in galactic cosmic rays.In order to identify particle properties,AMS-02 includes several specialized sub-detectors.Among these,the AMS-02 Ring Imaging Cherenkov detector(RICH) is designed to provide a very precise measurement of the velocity and electric charge of particles.We describe a method to reject the dominant electron background in antiproton identification with the use of the AMS-02 RICH detector as a veto for rigidities below 3 GV.A ray tracing integration method is used to maximize the statistics of  with the lowest possible e background,providing 4 times rejection power gain for e background with respect to only 3% of  signal efficiency loss.By using the collected cosmic-ray data,e contamination can be well suppressed within 3% with β≈ 1,while keeping 76% efficiency for  below the threshold.     

Proposal for muon and white neutron sources at CSNS

The China Spallation Neutron Source （CSNS） is a large scientific facility with the main purpose of serving multidisciplinary research on material characterization using neutron scattering techniques. The accelerator system is to provide a proton beam of 120 kW with a repetition rate of 25 Hz initially （CSNSⅠ）, progressively upgradeable to 240 kW （CSNS-Ⅱ） and 500 kW （CSNS-Ⅱ＇）. In addition to serving as a driving source for the spallation target, the proton beam can be exploited for serving additional functions both in fundamental and applied research. The expanded scientific application based on pulsed muons and fast neutrons is especially attractive in the overall consideration of CSNS upgrade options. A second target station that houses a muon-generating target and a fast-neutron-generating target in tandem, intercepting and removing a small part of the proton beam for the spallation target, is proposed. The muon and white neutron sources are operated principally in parasitic mode, leaving the main part of the beam directed to the spallation target. However, it is also possible to deliver the proton beam to the second target station in a dedicated mode for some special applications. Within the dual target configuration, the thin muon target placed upstream of the fast-neutron target will consume only about 5% of the beam traversed; the majority of the beam is used for fast-neutron production. A proton beam with a beam power of about 60 kW, an energy of 1.6 GeV and a repetition rate of 12.5 Hz will make the muon source and the white neutron source very attractive to multidisciplinary researchers.     

Proposal for muon and white neutron sources at CSNS

The China Spallation Neutron Source (CSNS) is a large scientific facility with the main purpose of serving multidisciplinary research on material characterization using neutron scattering techniques. The accelerator system is to provide a proton beam of 120 kW with a repetition rate of 25 Hz initially (CSNSⅠ), progressively upgradeable to 240 kW (CSNS-Ⅱ) and 500 kW (CSNS-Ⅱ'). In addition to serving as a driving source for the spallation target, the proton beam can be exploited for serving additional functions both in fundamental and applied research. The expanded scientific application based on pulsed muons and fast neutrons is especially attractive in the overall consideration of CSNS upgrade options. A second target station that houses a muon-generating target and a fast-neutron-generating target in tandem, intercepting and removing a small part of the proton beam for the spallation target, is proposed. The muon and white neutron sources are operated principally in parasitic mode, leaving the main part of the beam directed to the spallation target. However, it is also possible to deliver the proton beam to the second target station in a dedicated mode for some special applications. Within the dual target configuration, the thin muon target placed upstream of the fast-neutron target will consume only about 5% of the beam traversed; the majority of the beam is used for fast-neutron production. A proton beam with a beam power of about 60 kW, an energy of 1.6 GeV and a repetition rate of 12.5 Hz will make the muon source and the white neutron source very attractive to multidisciplinary researchers.     

An Approach to Extract the Spin Transfer to ∧in Polarized Proton--Proton Collision

We introduce an approach to extract the spin transfer to A in polarized proton-proton collision, based on the relation between single spin asymmetry and the polarization of A production. With 4 × 10^6 ∧ events simulated for a PHENIX detector system, DLL = 0.1598 ± 0.0343 is retrieved by the approach and it agrees very well with the input value of 0.1429. The approach is further tested and confirmed with ‘bunch shuffling＇ method for the simulated events as well as experimental events collected at PHENIX in 2003. It is concluded that one can correctly extract the spin transfer without detailed understanding of acceptance correction even if the correction is significantly large in PHENIX experiment by using the approach described here. The method can be generally used for spin transfer study.     

Development of Yangbajing air shower core detector for a new EAS hybrid experiment

Aiming at the observation of cosmic-ray chemical composition in the "knee" energy region, we have been developing a new type of air-shower core detector(YAC, Yangbajing Air shower Core detector array) to be set up at Yangbajing(90.522?E, 30.102?N, 4300 m above sea level, atmospheric depth: 606 g/m2) in Tibet, China.YAC works together with the Tibet air-shower array(Tibet-Ⅲ) and an underground water Cherenkov muon detector array(MD) as a hybrid experiment.Each YAC detector unit consists of lead plates of 3.5 cm thickness and a scintillation counter which detects the burst size induced by high energy particles in the air-shower cores.The burst size can be measured from 1 MIP(Minimum Ionization Particle) to 106 MIPs.The first phase of this experiment, named"YAC-Ⅱ ", consists of 16 YAC detectors each with a size of 40 cm×50 cm and distributed in a grid with an effective area of 10 m2.YAC-Ⅱ is used to check hadronic interaction models.The second phase of the experiment, called"YAC-Ⅱ ", consists of 124 YAC detectors with coverage of about 500 m2.The inner 100 detectors of 80 cm×50 cm each are deployed in a 10×10 matrix with a 1.9 m separation; the outer 24 detectors of 100 cm×50 cm each are distributed around these to reject non-core events whose shower cores are far from the YAC-Ⅱ array.YAC-Ⅱ is used to study the primary cosmic-ray composition, in particular, to obtain the energy spectra of protons, helium and iron nuclei between 5×1013eV and 1016 eV, covering the "knee" and also connected with direct observations at energies around 100 TeV.We present the design and performance of YAC-Ⅱ in this paper.     

Simulation of the Galactic Cosmic Ray Shadow of the Sun

The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space,and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise.A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth–Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.     

Design and application of a laser beam alignment system based on the imaging properties of a multi-pass amplifier

Image relaying is presented as a technique for aligning beams onto mm-sized target of high power laser. On the basis of summarizing the preceeding work on the near-field image relaying of multiple spatial filters, the far-filed image relaying is suggested firstly. The near-field and far-field image relaying properties of multiple spatial filters in laser beams automatic alignment system are analyzed. A geometrical optics approach and an ABCD ray matrix theory are used throughout. The reasonable and optimum scheme for automatically aligning multi-pass beam paths is presented and demonstrated on the multi-pass amplifier system of the SG-Ⅲprototype.