status of de/dx offline software
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Status of dE/dx Offline Software
WANG Dayongwangdy@mail.ihep.ac.cn
Institute of High Energy PhysicsJan 10,2006
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
dE/dx :Particle ID with energy loss measurements
Principle: P = · mImplementation: C++ programming under BOSS
frameworkComponents: MdcDedxAlg, DedxCalibAlg, Dedx
CorrecSvcDesign goal: Resolution 6—7%, good seperation
MDC
tracking
dE/dx~f(v)
Particle type info
Requirements and data flow
MDC Tracking
dE/dx Reconstruction
Global Particle Identification
TransientData Store
(TDS)
MDC digits
Tracks
MDC digitsTracks
Recon dE/dx
Recon dE/dx
partId info
physics analysis Real dataflow
Apparent dataflow
Tracks
Recon dE/dx
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
Overview of the software
MdcDedxReconDedxCalibAlg
Calibrationconst
CalibDataSvc
DedxCorrecSvc
EventDataSvc
Transient DataStore
Transient CalibData Store
DST
converter
converter
<<uses>>
<<uses>>
<<uses>>
<<uses>>
<<uses>>
MdcGeomSvc
<<uses>> <<uses>>
dE/dx calibration package
+i ni t i al i se()+execute()+fi nal i se()+BookHi sts()+Fi l l Hi sts()+Anal yseHi sts()+Wri teHi sts()+getChargeOff Corr()+ReadParameters()+Wri teParameters()
DedxCal i b
Al gori thm
DedxCal i bLayerGai n DedxCal i bDri ftDi st DedxCal i bSaturati on DedxCal i bZposDedxCal i bWi reGai n DedxCal i bRunByRun
DedxCal i bParameters<<uses>>
DedxCalibAlg
DedxCorrecSvc+queryI nterface()
I Interface
+setProperty()+getProperty()
IProperty
+StandardCorrec()+Wi reGai nCorrec()+Dri f tDi stCorrec()+SaturCorrec()+ZdepCorrec()+LayerGai nCorrec()+Gl obal Correc()+PathL()
-m_run-m_cal i b_fl ag-m_cal i b_const
DedxCorrecSvc
+name()+i ni t i al i ze()+fi nal i ze()
IServi ce
Servi ce
+StandardCorrec()
IDedxCorrecSvc
MdcGeomSvc
Cal i bSvc
<<uses>>
<<uses>>
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;
Sys. effects and dE/dx corrections
① Gain variations among cells
② Sampling length corrections
③ Drift distance dependence
④ Longitude position(z) dependence
⑤ Space charge effect
⑥ Charge gain non-linearity: from electronics
⑦ Corrections related to particle type
⑧ Run by run pulse height correction:Dependence on the sense wire voltage , temperature, pressure and other environmental effects…
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
)cos
(1
)cos
('
Q
Q
These parameterizations are to be tested by long-model data analysis
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
Landau formula X P2~0 4-par fit X
BESIII Simulation Preliminary
Global 5-parameter fit for phmp_nml vs
5
44
13ln2
1p
pp
ppp
dx
dE
binning with nearly the same statisticsat each point to reduce the errorUsing garbage events in order to fastly calibrate this curve for BESIII in futureA uniform formula to avoid discrete expression for density effect The curve fit the BESII data OK
Beam-gas proton
Cosmic rays
Radiative bb
BESII data
1. In whole BesIII momentum range: 0.15—2GeV/c, good uniformity is seen with different particles and with momentum overlap;
2. Quality of curve fitting is good in the whole range
3. The fitting results is quite stable
The best dE/dx curve obtained
5
44
13ln2
1p
pp
ppp
dx
dE
BESIII Simulation Preliminary
Algorithm studies: different estimation of most probable energy
lossLandau distribution has no definite mean. The algorithm use
d 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
idea:these methods give less bias to large values,then the satured hits have less effect to give better shape and better seperation
Different estimation of most probable energy loss: resolution
5.51% 5.34%
6.06% 5.09%
5.75% 5.44%
5.71% 2.61%
BOOST MC, MIP muon
Truncation rate: 0.7
Different estimation of most probable energy loss: seperation power
Pi/K Pi/P
0.7GeV 1.2GeV
Pi/K Pi/P 0.7GeV 1.3GeV
Pi/K Pi/P
0.7GeV 1.3GeV
Pi/K Pi/P
0.75GeV 1.3GeV
BOOST MC, MIP muon
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
0.75GeV 1.3GeV
Comparison of linear&logorithm TM
Cosmic rays Radiative Bhabha
Pull width: 1.020 0.9995 Pull width: 0.8477 0.9304
shape is more Gaussian-like shape is more Gaussian-like
Logorithm TM(right figure),compared to plain TM(left figure):
Suppress high-end residual Landau tail
The distribution more Gaussian likeBESII DATA, J/Psi hadrons
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
After truncation, distribution just Gaussian-like
Landau tail
BOOST MC, 1GeV electrons
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
Calibration of σdE/dx
35.2
0.8132.0
46.0
In
n
Empirical formula :
2
1153.0
t
A
Z
Q dependence of σdE/dx
σ /Q= p0+p1*ln ( Q ) ,p0,p1 is fitting parameters
Hits number and polar angle dependence
32.0-0.46 sin,n
σdE/dx~ polar angle relationship
0p1norm sinp
σdE/dx~ hits number relationship
0phit1norm Np
Present performance(I)
Software are robust
Basic calibration and correction,and need more
dE/dx resolution can reach design requirements: 6-7%
5.96%
χ distribution for Kaon sample Prob ( K ) distribution for Kaon sample
Present performance(II)
dxdE
mea dEdxdxdE
/
exp )/(
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
dE/dx seperation for 5 particles(MC) seperation power with dE/dx
Present performance(III)
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
summary OO designed dE/dx software is developed unde
r BOSS, released and used for physics Calibration algorithms and service are develop
ed 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
Thank you谢谢!
Backed -up slides…
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