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. Thi...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.展开更多
The decay channel ψ′→ π 〉+π^-J/ψ(J/ψ 〉 γp^-p) is studied using a sample of 1.06 × 10^8 ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p...The decay channel ψ′→ π 〉+π^-J/ψ(J/ψ 〉 γp^-p) is studied using a sample of 1.06 × 10^8 ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p^-p invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M = 1861-13^+6 (stat)-26^+7 (syst) MeV/c^2 and a narrow width that is Г 〈 38 MeV/c^2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.展开更多
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...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.展开更多
The principle of the method for the BESIII TOF calibration using cosmic ray data without magnetic field are reported in this paper. After applying calibration constants, the single-end readout time resolution could re...The principle of the method for the BESIII TOF calibration using cosmic ray data without magnetic field are reported in this paper. After applying calibration constants, the single-end readout time resolution could reach about 150 ps, and the time resolution for one layer is achieved to be about 110 ps. The paper also described the extraction scheme for the event start time of cosmic events.展开更多
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 simu...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.展开更多
This paper focuses mainly on the vertex reconstruction of resonance particles with a relatively long lifetime such as Ks^0, A, as well as on lifetime measurements using a 3-dimensional fit. The kinematic constraints b...This paper focuses mainly on the vertex reconstruction of resonance particles with a relatively long lifetime such as Ks^0, A, as well as on lifetime measurements using a 3-dimensional fit. The kinematic constraints between the production and decay vertices and the decay vertex fitting algorithm based on the least squares method are both presented. Reconstruction efficiencies including experimental resolutions are discussed. The results and systematic errors are calculated based on a Monte Carlo simulation.展开更多
The number of J/ψ events collected with the BES detector at the BEPC from June 12 to July 28, 2009 is determined to be (225.3 ± 2.8) × 10^ 6 using J/ψ→inclusive events, where the uncertainty is the syst...The number of J/ψ events collected with the BES detector at the BEPC from June 12 to July 28, 2009 is determined to be (225.3 ± 2.8) × 10^ 6 using J/ψ→inclusive events, where the uncertainty is the systematic error and the statistical one is negligible.展开更多
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 se...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.展开更多
基金Supported by National Natural Science Foundation of China (10821063, 10875141, 10705034, 10605030)Ministry of Science and Technology of China (2009CB825200)+1 种基金Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program (KJCX2-YW-N29, KJCX2-YW-N45)United States Department of Energy (DE-FG02-91ER40682)
文摘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.
基金Supported by Ministry of Science and Technology of China (2009CB825200)National Natural Science Foundation of China(NSFC) (10625524,10821063,10825524,10835001,10935007)+6 种基金Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program,CAS (KJCX2-YW-N29,KJCX2-YW-N45)100 Talents Program of CASIstituto Nazionale di Fisica Nucleare,Italy,Russian Foundation for Basic Research (08-02-2221, 08-02-92200-NSFC-a)Siberian Branch of Russian Academy of Science,joint project No 32 with CAS,Chinese University of Hong Kong Focused Investment Grant (3110031)U. S. Department of Energy(DE-FG02-04ER41291,DE-FG02-91ER40682,DE-FG02-94ER40823)WCU Program of National Research Foundation of Korea(R32-2008-000-10155-0)the A.P. Sloan Foundation
文摘The decay channel ψ′→ π 〉+π^-J/ψ(J/ψ 〉 γp^-p) is studied using a sample of 1.06 × 10^8 ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p^-p invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M = 1861-13^+6 (stat)-26^+7 (syst) MeV/c^2 and a narrow width that is Г 〈 38 MeV/c^2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.
基金Supported by National Natural Science Foundation of China (10821063, 10875141, 10705034, 10605030)Ministry of Science and Technology of China (2009CB825200)+1 种基金Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program (KJCX2-YW-N29, KJCX2-YW-N45)United States Department of Energy (DE-FG02-91ER40682)
文摘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.
基金Supported by National Natural Science Foundation of China (10565001, 10647002, 10875138)
文摘The principle of the method for the BESIII TOF calibration using cosmic ray data without magnetic field are reported in this paper. After applying calibration constants, the single-end readout time resolution could reach about 150 ps, and the time resolution for one layer is achieved to be about 110 ps. The paper also described the extraction scheme for the event start time of cosmic events.
基金Supported by National Natural Science Foundation of China (10675004, 10835001, 10491300, 10491303, 10735080)Research and Development Project of Important Scientific Equipment of CAS (H7292330S7)
文摘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.
基金Supported by CAS Knowledge Innovation Project (112901160333,111087513811)National Natural Science Foundation of China (10491300,10491303)100 Talents Program of CAS (U-25 and U-54)
文摘This paper focuses mainly on the vertex reconstruction of resonance particles with a relatively long lifetime such as Ks^0, A, as well as on lifetime measurements using a 3-dimensional fit. The kinematic constraints between the production and decay vertices and the decay vertex fitting algorithm based on the least squares method are both presented. Reconstruction efficiencies including experimental resolutions are discussed. The results and systematic errors are calculated based on a Monte Carlo simulation.
基金Supported by Ministry of Science and Technology of China (2009CB825200)National Natural Science Foundation of China (NSFC) (10625524, 10821063, 10825524, 10835001, 10935007, 11125525)+3 种基金Joint Funds of National Natural Science Foundation of China (11079008, 11179007)Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program (KJCX2-YW-N29, KJCX2-YW-N45)100 Talents Program of CAS, Istituto Nazionale di Fisica Nucleare, Italy, U. S. Department of Energy (DE-FG02-04ER41291, DE-FG02-91ER40682, DE-FG02-94ER40823)U.S. National Science Foundation, University of Groningen (RuG) and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt, WCU Program of National Research Foundation of Korea (R32-2008-000-10155-0)
文摘The number of J/ψ events collected with the BES detector at the BEPC from June 12 to July 28, 2009 is determined to be (225.3 ± 2.8) × 10^ 6 using J/ψ→inclusive events, where the uncertainty is the systematic error and the statistical one is negligible.
基金Supported by National Natural Science Foundation of China (10375002, 10675004, 10821063)Research and Development Project of Important Scientific Equipment of CAS (H7292330S7)
文摘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.