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.     

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.     

Study of BESⅢ MUC offline 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.     

Performance of the muon detector A under TIBET Ⅲ array

In order to observe gamma rays in the 100 TeV energy region, the 4500 m² underground muon detector array using water Cherenkov technique is constructed, forming the TIBET Ⅲ+MD hybrid array. Because the showers induced by primary gamma rays contain much fewer muons than those induced by primary hadrons, significant improvement of the gamma ray sensitivity for TIBET Ⅲ+MD array is expected. In this paper, the design and performance of the MD-A detector with large Tyvek bag is reported.     

Status of the Fermilab muon （g-2） experiment

The New Muon （g-2） Collaboration at Fermilab has proposed to measure the anomalous magnetic moment of the muon, αμ, a factor of four better than was done in E821 at the Brookhaven AGS, which obtained αμ = [116592089（63）] × 10^-11 ±0.54 ppm. The last digit of a, is changed from the published value owing to a new value of the ratio of the muon-to-proton magnetic moment that has become available. At present there appears to be a difference between the Standard-Model value and the measured value, at the ≌ 3 standard deviation level when electron-positron annihilation data are used to determine the lowest-order hadronic piece of the Standard Model contribution. The improved experiment, along with further advances in the determination of the hadronic contribution, should clarify this difference. Because of its ability to constrain the interpretation of discoveries made at the LHC, the improved measurement will be of significant value, whatever discoveries may come from the LHC.     

Determination of event start time at BESⅢ

The principle of the method for the BESⅢ event start time determination and the code construction are described. The investigation of influence of the noise, the method of rejecting noise and the performance checking by the Monte Carlo physics data sample are also presented. The preliminary results got from the Monte Carlo simulation are presented, the reconstruction efficiency of J/ψ→ anything events at noise level 0~60% can achieve above 99%, and the error rate is below 1%.     

Mini-review of rare charmonium decays at BESⅢ

Recently, the LHCb experiment announced 3.5σ evidence for direct CP violation in D⁰ decay by looking at the difference between A_CP(D⁰→K⁺K^-) and A_CP(D⁰→π⁺π^-). This is the rst evidence of CP violation in a charm system, which may indicate new physics beyond the Standard Model. Motivated by this measurement, we review rare processes in charmonium decay, especially, the weak decay, C or P violated decay, and lepton avor violated decays. In case the new physics appears in charm sector, these rare decays of charmonium states will provide an opportunity to search for signi cant contributions from physics beyond the Standard Model. With huge J/ψ and ψ(2S) samples in BES0 experiment, the rare decays may be feasible.     

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.     

Significance of absolute energy scale for physics at BESⅢ

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.     

水基切伦科夫μ子探测器的研究

利用高速带电粒子在透明介质中产生切伦科夫辐射的特性,以蒸馏水作为辐射介质,搭建了一个小尺寸(π×22.52cm2×45 cm)的切伦科夫探测器,对能量在GeV量级的μ子进行了相应的测量,考虑其他能量损耗、光传输和收集效率、阴极量子效率后,实验结果与理论估计值有比较高的相符度,可以初步断定仪器具备探测GeV量级μ子的能力.     

Study of tracking efficiency and its systematic uncertainty from J/ψ→ppπ~+π~- at BESIII

Based on J/ψ events collected with the BESIII detector,with corresponding Monte Carlo samples,the tracking efficiency and its systematic uncertainty are studied using a control sample of J/ψ→ppπ~+π~-.Validation methods and different factors influencing the tracking efficiency are presented in detail.The tracking efficiency and its systematic uncertainty for protons and pions with the transverse momentum and polar angle dependence are also discussed.     

Calibration of CR-39 solid state nuclear track detector

Nowadays there are increasing uses of SSNTD on scientific works in Thailand. Currently we are using SSNTD as an important tool for confirming active fault zones in a province in which a new nuclear research reactor has been proposed to come up. Soil gas radon was measured by both active and passive methods. In the latter case CR-39 SSNTD was installed in a PVC tube of 50 cm long by 5 cm in diameter. The tubes were placed in 50-cm deep holes lining perpendicular to the faults’ trace for one week. In this paper we describe the method and the results on calibrating these detectors using a radon chamber and a NIST-traceable radium-226 standard source.      

双极晶体管中子注量探测器的标定

双极晶体管经中子辐照后会引起直流增益退化,在10⁹~10¹⁶ cm^-2的注量范围内,其直流增益倒数变化与辐照中子注量呈线性关系。对直流增益退化的双极晶体管进行高温退火,能使受到辐射损伤的双极晶体管性能恢复。鉴于此,将双极晶体管进行逆向工程应用,制作成中子注量探测器,经标定后,可实现对中子注量的监测。对探测器的装配结构进行设计后,依托中国工程物理研究院快中子脉冲堆(CFBR-Ⅱ),在10¹²~10¹³ cm^-2的注量范围对3DK2222A型探测器和在10¹³ cm^-2的注量范围对3DG121C型探测器进行标定。在得到探测器损伤常数K的分散性存在较小和较大的两种情况下,确定了分散性较小时的有效取值和应用方法,以及在分散性较大时,采取标定的损伤常数K只能应用在同只探测器上的方案,并通过高温退火实验证实了该方案的可行性。     

Study of cluster reconstruction and track fitting algorithms for CGEM-IT at BESIII

Considering the effects of aging on the existing Inner Drift Chamber(IDC) of BESIII, a GEM-based inner tracker, the Cylindrical-GEM Inner Tracker(CGEM-IT), is proposed to be designed and constructed as an upgrade candidate for the IDC. This paper introduces a full simulation package for the CGEM-IT with a simplified digitization model, and describes the development of software for cluster reconstruction and track fitting, using a track fitting algorithm based on the Kalman filter method. Preliminary results for the reconstruction algorithms which are obtained using a Monte Carlo sample of single muon events in the CGEM-IT, show that the CGEM-IT has comparable momentum resolution and transverse vertex resolution to the IDC, and a better z-direction resolution than the IDC.     

High intensity muon/pion beam with time structure at PSI

A new initiative is presented to develop a high intensity muon/pion beam with a time structure optimized to the muon lifetime. Such a facility would provide exciting physics opportunities for dramatically improved fundamental experiments, e.g., in the field of muon capture, muon lifetime and muonium spectroscopy. The high primary beam intensity at PSI allows intense chopped muon beams by installing a fast electrostatic kicker in a secondary channel. Two modes of operation are foreseen: a muon-on-request scheme, which uses active feedback from a beam counter in the experimental area and a periodic pulsed mode with about 5–20% duty factor. This revised version was published online in August 2006 with corrections to the Cover Date.     

大型强子对撞机上的CMS探测器

CMS探测器是大型强子对撞机（LHC）上的4个实验之一,它的设计思想是在质心能量为14TeV及积分亮度为1034 cm-2s-1的条件下对质子-质子对撞进行研究.它的特点是非常紧凑,其μ子室几乎覆盖了4π立体角.另外,CMS探测器还有可提供超强磁场的超导磁铁和由超导磁铁环绕的径迹室以及电磁量能器和强子量能器.CMS探测器对于末态为电子、光子、特别是μ子的物理过程有很好的测量精度.     

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.