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Status of dE/dx Offline Software

Status of dE/dx Offline Software. WANG Dayong wangdy@mail.ihep.ac.cn Institute of High Energy Physics Jan 10,2006. Outline. dE/dx software :OO design and development MdcDedxAlg : Reconstruction DedxCalibAlg : Calibration DedxCorrecSvc : Public service for dE/dx correction

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Status of dE/dx Offline Software

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  1. Status of dE/dx Offline Software WANG Dayong wangdy@mail.ihep.ac.cn Institute of High Energy Physics Jan 10,2006

  2. Outline • dE/dx software :OO design and development • MdcDedxAlg : Reconstruction • DedxCalibAlg : Calibration • DedxCorrecSvc : Public service for dE/dx correction • Calibration and systematic corrections • Important systematic and enviromental effects • Calibration parameteriazation • Reconstruction algorithm studies: • Different estimation of most prob Eloss • Ionization Curve studies • Resolution and residual bias correction • Summary

  3. dE/dx :Particle ID with energy loss measurements dE/dx~f(v) Particle type info • Principle: P = · m • Implementation: C++ programming under BOSS framework • Components: MdcDedxAlg, DedxCalibAlg, DedxCorrecSvc • Design goal: Resolution 6—7%, good seperation MDC tracking

  4. Requirements and data flow MDC digits • AIM: to give the partID information from the list of pulse heights of hits on the MDC track, and store them into TDS • some corrections are performed to get unbiased dE/dx information. • Some proper dE/dx estimators are constructed MDC digits Transient Data Store (TDS) MDC Tracking Tracks Tracks MDC digits Tracks dE/dx Reconstruction Recon dE/dx Recon dE/dx Recon dE/dx Global Particle Identification partId info Apparent dataflow 。。。 Real dataflow physics analysis

  5. Overview of the software

  6. dE/dx calibration package DedxCalibAlg

  7. DedxCorrecSvc

  8. Calibration data structure double m_wireg[6860]; double m_ggs[4][43]; double m_ddg[4][43]; double m_zdep[4][43]; double m_layerg[43]; double m_gain; double m_resol;

  9. Sys. effects and dE/dx corrections • Gain variations among cells • Sampling length corrections • Drift distance dependence • Longitude position(z) dependence • Space charge effect • Charge gain non-linearity: from electronics • Corrections related to particle type • Run by run pulse height correction:Dependence on the sense wire voltage ，temperature, pressure and other environmental effects…

  10. Parameterizations in calibration • Gas gain: • Standard Landau distribution • Vavilov distribution • Asymmetric Gaussian distribution: • Space charge effect: general form of Q’=Q/(1-k(θ)*Q) • BesII: fit with polynomial：a=F(40°)/F(θ) Q’=Q*a • CLEOII formulation: δ:longitude range of avalanche • Babar formulation: • Parameterization of other effects: • 3 order polynomials (presently implemented) • Chebyshev series with the 1st kind of Chebyshev polynomials These parameterizations are to be tested by long-model data analysis

  11. Comparison and choice of dE/dx curve • Sternheimer(A) is better at high momentum end • Va’vra(B) is relative better at low momentum end • Practical global parameterization of curve is prefered Comparison of Sternheimer and Va’vra formula: A B BESIII Simulation Preliminary Landau formula X P2~0 4-par fit X

  12. Global 5-parameter fit for phmp_nml vs • binning with nearly the same statisticsat each point to reduce the error • Using garbage events in order to fastly calibrate this curve for BESIII in future • A uniform formula to avoid discrete expression for density effect • The curve fit the BESII data OK Beam-gas proton Radiative bb Cosmic rays BESII data

  13. The best dE/dx curve obtained BESIII Simulation Preliminary • In whole BesIII momentum range: 0.15—2GeV/c, good uniformity is seen with different particles and with momentum overlap; • Quality of curve fitting is good in the whole range • The fitting results is quite stable

  14. Landau distribution has no definite mean. The algorithm used must estimate the most probable energy loss Truncated mean Double truncated mean: truncate at both ends Median Geometric mean Harmonic mean Transformation: Logorithm truncated mean: studies based on BESII data Algorithm studies: different estimation of most probable energy loss idea:these methods give less bias to large values,then the satured hits have less effect to give better shape and better seperation

  15. Different estimation of most probable energy loss: resolution 5.51% 5.34% 5.44% 5.75% 6.06% 2.61% 5.09% 5.71% BOOST MC, MIP muon Truncation rate: 0.7

  16. Different estimation of most probable energy loss: seperation power Pi/K Pi/P 0.7GeV 1.3GeV Pi/K Pi/P 0.7GeV 1.2GeV Pi/K Pi/P 0.7GeV 1.2GeV Pi/K Pi/P 0.7GeV 1.2GeV Pi/K Pi/P 0.6GeV 1.1GeV Pi/K Pi/P 0.7GeV 1.3GeV Pi/K Pi/P 0.75GeV 1.3GeV Pi/K Pi/P 0.75GeV 1.3GeV BOOST MC, MIP muon

  17. Comparison of linear&logorithm TM • Logorithm TM(right figure),compared to plain TM(left figure): • Suppress high-end residual Landau tail • The distribution more Gaussian like BESII DATA, J/Psi hadrons shape is more Gaussian-like shape is more Gaussian-like Pull width: 1.020 0.9995 Pull width: 0.8477 0.9304 Cosmic rays Radiative Bhabha

  18. Study of truncated mean method • Well established method of dE/dx estimation • Simple and robust • Rejection of lower end hits to remove contributions from noise and background fluctuation • Truncation of higher tail to remove Landau tail due to hard collisions Just cooresponding to ~5% lower cut Landau tail After truncation, distribution just Gaussian-like BOOST MC, 1GeV electrons

  19. Resolution curve with different truncation rates • 70% truncation ratio is adopted for the algorthm • Number of good hits is required to no less than 10 for each track • Resolution from perfect MC consistent with empirical formula BOOST MC, 1GeV electrons

  20. Calibration of σdE/dx • Q dependence of σdE/dx • σ /Q= p0+p1*ln（Q） ， • p0,p1 is fitting parameters • Hits number and polar angle dependence Empirical formula :

  21. σdE/dx~ polar angle relationship

  22. σdE/dx~hits number relationship

  23. Present performance(I) 5.96% • Software are robust • Basic calibration and correction,and need more • dE/dx resolution can reach design requirements: 6-7%

  24. Present performance(II) χ distribution for Kaon sample Prob（K）distribution for Kaon sample • Distribution of is nearly a normal N(0,1)distribution • Distributions of probability function are flat • Our estimation is unbiased and can provide good partId info

  25. Present performance(III) dE/dx seperation for 5 particles(MC) seperation power with dE/dx • Good particle seperation in a wide range for different particles • The important π/K seperation(3 σ )can reach nearly 800MeV/c • Particle identification efficiency is more than 90% with MC samples

  26. summary • OO designed dE/dx software is developed under BOSS, released and used for physics • Calibration algorithms and service are developed and many corrections performed to get unbiased estimation of dE/dx • Different reconstruction algorithms are explored to get best performance • Particle id is tested with MC samples, dE/dx resolution, distributions, pid efficiency is satisfactory. • To reach BESIII design goals, there are still much to understand and deal with

  27. Thank you谢谢！ Backed -up slides…

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