Bian Jian-Ming

Lagrange multiplier method used in BESIII kinematic fitting

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 impr...

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%.

Study of the online event filtering algorithm for BESIII

The results of a study of event tagging strategies for elementary physics processes in the τ-charm region are presented. The algorithm for online event filtering is optimized by adopting the information provided by different sub-detectors according to their strengths and capacities. The algorithm is tested with various generated physics and background events. The results indicate that the algorithm satisfies the requirements of BESIII physics analysis and its DAQ system.

Decay vertex reconstruction and 3-dimensional lifetime determination at BESIII

This paper focuses mainly on the vertex reconstruction of resonance particles with a relatively long lifetime such as K0S, Λ, 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.

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.

Track reconstruction using the TSF method for the BESIII main drift chamber

We describe the algorithm to reconstruct the charged tracks for BESIII main drift chamber at BEPCII, including the track finding and fitting. With a new method of the Track Segment Finder (TSF), the results of present study indicate that the algorithm can reconstruct the charged tracks over a wide range of momentum with high efficiency, while improving the robustness against the background noise in the drift chamber. The overall performances, including spatial resolution, momentum resolution and secondary vertices reconstruction efficiency, etc. satisfy the requirements of BESIII experiment.

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.

Energy loss correction for a crystal calorimeter

Material effect of inner-detectors on the performances of the BESIII Electromagnetic Calorimeter (EMC) is investigated. The BESIII Time-Of-Flight counters (TOF) have been utilized to improve the energy resolution and detection efficiency for photons after a careful energy calibration. A matching algorithm between TOF and EMC energy deposits is developed, and the effects of beam-related background are discussed. The energy resolution is improved and the photon detection efficiency can be increased by the combined measurement of EMC and TOF detectors.

Studyof hc(1P1) at BESIII

Inclusive measurements of the spin-singlet P-wave state of charmonium h{sub c}({sup 1}P{sub 1}) have been performed with a sample of approximately 106 million {psi}(2S) decays collected with the BESIII detector at the BEPCII electron-positron storage ring. We fitted distributions of the mass recoiling against the {pi}{sup 0} in the decay {psi}(2S){pi}{sup 0}h{sub c} both inclusively and with a tag of the E1-transition photon from h{sub c{yields}{gamma}{eta}c} to obtain the following preliminary results:M(h{sub c}) = 3525.16{+-}0.16(stat.) MeV, {Gamma}(h{sub c}) = 0.89{+-}0.57(stat.) MeV, B({psi}(2S){yields}{pi}{sup 0}h{sub c}) = (8.42{+-}1.29(stat.))x10{sup -4}, B({psi}(2S){yields}{pi}{sup 0}h{sub c})xB(h{sub c{yields}{gamma}{eta}c}) = (4.69{+-}0.48(stat.)x10{sup -4}, and B(h{sub c{yields}{gamma}{eta}c}) = (55.7{+-}6.3(stat.))%.Inclusive measurements of the spin‐singlet P‐wave state of charmonium hc(1P1) have been performed with a sample of approximately 106 million ψ(2S) decays collected with the BESIII detector at the BEPCII electron‐positron storage ring. We fitted distributions of the mass recoiling against the π0 in the decay ψ(2S)π0hc both inclusively and with a tag of the E1‐transition photon from hc→γηc to obtain the following preliminary results:M(hc) = 3525.16±0.16(stat.) MeV, Γ(hc) = 0.89±0.57(stat.) MeV, B(ψ(2S)→π0hc) = (8.42±1.29(stat.))×10−4, B(ψ(2S)→π0hc)×B(hc→γηc) = (4.69±0.48(stat.)×10−4, and B(hc→γηc) = (55.7±6.3(stat.))%.

BESIII barrel time-of-flight （TOF） calibration using cosmic ray data

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 p...