Some topics on charmonium decays at BESⅢ experiment

The construction of BESⅢ detector has been finished and the data taking is under plan. Some physics topics on charmonium decays at BESⅢ experiment are discussed in this paper. The measurement of properties of η_c and η_c at BESⅢ is discussed and the expected precision of the measurement is estimated based on BOSS. Also the χ_cJ decay and the measurement of hyperon decay parameters are mentioned.     

Event generators at BESⅢ

We present a brief remark and introduction to event generators for tau-charm physics currently used at BESⅢ,including KKMC,BesEvtGen,Bhlumi,Bhwide,Babayaga and inclusive Monte-Carlo event generators.This paper provides basic information on event generators for BESⅢ users.     

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.     

D0-D0 mixing and CP violation at BES-Ⅲ

Recently, both BaBar and Belle experiments found evidences of neutral D mixing. In this paper, we discuss the sensitivities of the measurements of D mixing parameters at BESⅢ. With CP tag technique at ψ(3770) peak, the extraction of the strong phase difference in D⁰ →Kπ decay at BESⅢ are     

Event generators at BESⅢ

We present a brief remark and introduction to event generators for tau-charm physics currently used at BESⅢ, including KKMC, BesEvtGen, Bhlumi, Bhwide, Babayaga and inclusive Monte-Carlo event generators. This paper provides basic information on event generators for BESⅢ users.     

Study of the efficiency of event start time determination at BESⅢ

A method to estimate the efficiency of event start time determination at BESIII is developed.This method estimates the efficiency at the event level by combining the efficiencies of various tracks(e,μ,π,K,p,γ)in a Bayesian way.Efficiencies results and the difference between data and MC at the track level are presented in this paper.For a given physics channel,event start time efficiency and systematic error can be estimated following this method.     

The study of B→K*l+l- decays in family non-universal Z′ models

In a combined investigation of B → K ( * ) l + l - decays, constraints on the related couplings in family non-universal Z′ models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the B → K * l + l - decay can be explained by flipping the signs of the Wilson coefficients C eff 9 and C 10 . With the obtained constraints, we also calculate the branching ratio of the B s →μ + μ - decay. The upper bound of our prediction is nearly an order of magnitude smaller than the upper bound given by the CDF Collaboration recently.     

The study of B→K()l+l- decays in family non-universal Z' models

In a combined investigation of B→K^(*)l⁺l^- decays, constraints on the related couplings in family non-universal Z' models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the B→K^(*)l⁺l^- decay can be explained by flipping the signs of the Wilson coefficients C₉^eff and C₁₀. With the obtained constraints, we also calculate the branching ratio of the B_s→μ⁺μ^- decay. The upper bound of our prediction is nearly an order of magnitude smaller than the upper bound given by the CDF Collaboration recently.     

A photon conversion finder at BESⅢ

A photon conversion finder (PCF) based on track information from the main drift chamber (MDC) of the Beijing Spectrometer (BES0) at the Beijing Electron Positron Collider (BEPC/) is developed. The validation of the PCF is done by reconstructing π⁰ and measuring the branching fraction of J/ψ →γη'. Using the developed PCF tool, we mapped the materials from the interaction point through the BEPCII beam pipe up to the inner wall of the MDC.     

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.     

Tuning of the cosmic-ray test system of the BESⅢ drift chamber

The BESⅢ drift chamber and its subsystems need a cosmic-ray test after the chamber construction to check the chamber construction quality,testing the joint operation of the whole system and the performance of the chamber.The noise performance,drift time and charge measurements,and the scanning of channels were examined specifically.The preliminary results of the test indicate that the whole system works well.     

Improvement of main drift chamber Monte-Carlo tuning model at BESⅢ

Based on real data,a new parameterized model of the main drift chamber response is proposed.In this model,we tune the ratio of good hits and the residual distribution separately.By data quality checking,the diference between simulation and data in track reconstruction efciency reduces from 1%to 0.5%averagely for the pion in J/ψ→π+ππ0,and the momentum resolution agreement improves significantly for the proton in J/ψ→ppˉ.     

Testing lepton flavor universality in terms of BESⅢ and charm-tau factory data

The recent measurements on R_K and R_π imply that there exists a possible violation of the leptonic flavor universality which is one of the cornerstones of the Standard Model. It is suggested that a mixing between sterile and active neutrinos might induce such a violation. In this work we consider the scenarios with one or two sterile neutrinos to explicitly realize the data while the constraints from the available experiments have been taken into account. Moreover, as indicated in literature, the deviation of the real PMNS matrix from the symmetric patterns may be due to a μ-τ asymmetry, therefore the measurements on R_D(Ds)eμ=Γ(D(D_s)→ e⁺ν_e)/Γ(D(D_s)→ μ⁺ν_μ) and R_D(Ds)μτ=Γ(D(D_s)→ μ⁺ν_μ)/Γ(D(D_s)→ τ⁺ν_τ) (and for some other heavy mesons B^± and B_c etc.) may shed more light on the physics responsible for the violation of the leptonic flavor universality. The data of BESⅢ are available to test the universality and that of future charm-tau factories will provide more accurate information. In this work, we will discuss R_D(Ds)eμ and R_D(Ds)μτ in detail and also briefly consider the cases for B^± and B_c.     

D~0 -~0 mixing and CP violation at BES-Ⅲ

Recently,both BaBar and Belle experiments found evidences of neutral D mixing.In this paper, we discuss the sensitivities of the measurements of D mixing parameters at BES-Ⅲ.With CP tag technique atψ(3770)peak,the extraction of the strong phase difference in D~0→Kπdecay at BES-Ⅲare discussed.We also make an estimate on the measurements of the mixing rate R_M by using the coherent data atψ(3770)peak. The CP violation in D system is predicted with an unobserved level in the Standard Model.Any significant CP violation in the D system indicates the existence of new physics.The sensitivity of the measurements of CP violation in the D system is estimated in the coherent D decays.Finally,the search for the rare D decays are discussed,in which some of the forbidden decays are smoking gun of new physics.     

BESⅢ RPC宇宙线测试系统

北京谱仪(BESⅢ)采用阻性板室(Resistive Plate Chambers)作为其muon探测器, 总使用面积达1200m². 为保证探测器的质量, 每一块阻性板室都要求通过宇宙线测试. 宇宙线测试系统使用3个流光管室作为其触发和寻迹系统, 其空间分辨可达2—3mm, 覆盖面积约4m², 测试系统可同时测量8块RPCs. 最后, 还报道了RPC的初次测试结果.     

Effects of vector leptoquarks onΛb→Λ,lv^-l decay

Experimental data on R(D⁺).R(K⁺),and R(J/ψ),provided by different collaborations,show sizable deviations from the standard model predictions.To describe these anomalies,many new physics scenarios have been proposed.One of them is the leptoquark model,which introduces the simultaneous coupling of vector and scalar leptoquarks to quarks and leptons.To look for similar possible anomalies in the baryonic sector,we investigate the effects of a vector leptoquark U3(3,3,2/3)on various physical quantities related to the tree-levelΛb→Λclv^-l decays(l=u,t),which proceed via b→c l v^-l transiti ons at the quark level.We calculate the differential branching ratio,forward-backward asymmetry,and longitudinal polarizations of leptons and Ac baryons at theμandτlepton channels in the leptoquark model and compare their behavior to the predictions of the SM in terms of q^2.In the calculations,we use the form factors calculated in full QCD as the main input and account for all errors coming from the form factors and model parameters.We observe that at theτchanneL the Ra fit solution to data related to the leptoquark model sweeps some regions out of the SM band;nevertheless,the fit has a considerable intersection with the SM predictions.The Rr type solution gives roughly the same results as the SM on DBR(q^2)-q^2.At theμchannel.the leptoquark model gives results that are consistent with the SM predictions and existing experimental data on the behavior of DBR(q^2)with respect to q^2.Concerning the q^2 behavior of the AFB(q^2),the two types of fits forτand the predictions at the“channel in the leptoquark model give exactly the same results as the SM.We also investigate the behavior of the parameter R(q^2)with respect to q^2 and the value of R(Λc)in both the vector leptoquark and SM models.Both fit solutions lead to results that deviate considerably from the SM predictions for R(q^2)-q^2 and R(Ac).Future experimental data on R(q^2)-q^2 and RC made available by measurements of theΛb→Λcτv^-τchannel,will be particularly helpful.Any experimental deviations from the SM predictions in this channel would emphasize the im porta nee of tree-level hadronic weak tran sitions as good probes of new physics effects beyond the SM.     

Monte Carlo study on the low momentum μ-π identification of the BESⅢ EM calorimeter

The BESⅢ detector has a high-resolution electromagnetic calorimeter which can be used for low momentum μ-π identification.Based on Monte Carlo simulations, μ-π separation was studied.A multilayer perceptron neural network making use of the defined variables was used to do the identification and a good μ-π separation result was obtained.     

面向对象的BESⅢ探测器模拟系统

BESⅢ探测器的模拟软件包BOOST, 是基于Geant4开发的面向对象的模拟软件. BOOST全面地模拟了BESⅢ探测器的物质和几何结构, 给出了粒子在各个子探测器中的击中信息, 以ASCII码文件的形式输出原始数据和MC truth信息可供重建软件开发和物理分析使用, 初步结果显示BOOST的模拟是合理的.     

Test of BESⅢ RPC in the avalanche mode

The installation of the BESⅢ RPC system has been completed. Cosmic ray test results show that they perform very well in streamer mode and meet the BESⅢ requirements. We have tested several RPCs in the avalanche mode with the addition of extra SF₆ in the gas mixture. We find an efficiency plateau that reaches ～95%, and a time resolution of 1.8 ns. This demonstrates that the BESⅢ-type RPC can work in the avalanche mode as well.     

BESⅢ端盖TOF探测器的研制

针对BESⅢ端盖TOF的研制方案, 设计和制作了特殊构型的闪烁探测器. 研究了光电倍增管(R5924)和塑料闪烁体(BC404, BC408, EJ204)的性能. 测量了几种包装材料对单个闪烁探测器模块光收集和本征时间分辨的影响. 使用800MeV实验电子束对探测器模块的测量结果显示, 采用EJ204和BC404晶体其时间分辨小于80ps; 采用ESR材料包装可获得较大的输出信号, 提高了探测器的性能.