10/26/2006 JSPS Meeting @ KEK 1
Recent PFA Performance and Higgs Study using Kinematical Fit
JSPS Creative Scientific ResearchMonthly Meeting @ KEKOct. 26th, 2006
Tamaki Yoshioka ICEPP, Univ. of TokyoOn behalf of GLD Colleagues
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Introduction- Most of the important physics processes to be studied in the ILC experiment have multi-jets in the final state. → Jet energy resolution is the key in the ILC physics.
- The best energy resolution is obtained by reconstructing momenta of individual particles avoiding double counting among Trackers and Calorimeters.
- Charged particles (~60%) measured by Tracker.- Photons (~30%) by electromagnetic CAL (ECAL).- Neutral hadrons (~10%) by ECAL + hadron CAL (HCAL).
→ Particle Flow Algorithm (PFA)
- In this talk, general scheme and performance of the GLD-PFA, using the GEANT4-based full simulator (Jupiter), will be presented.
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Geometry in Jupiter
Muon Detector
Solenoid
Hadron Calorimeter (HCAL)
Electromagnetic Calorimeter (ECAL)
TPC
VTX, IT
As of August 06
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229.8cm
349.4cm
299.8cm419.4cm
Readout Line =10cm
270cm
Endcap.InnerRadius=40cm
BarrelHD
BarrelEM
EndcapEM
EndcapHD
Barrel.InnerRadius=210cm
Barrel.HalfZ=280cm
210cm
280cm
Calorimeter Geometry in Jupiter
IP
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Calorimeter Structure
ECALW/Scinti./Gap
3/2/1 (mm) x 33 layers
HCALFe/Scinti./Gap
20/5/1 (mm) x 46 layers
Absorber
Active Layer
Current cell size :2x2cm
Can be changed.
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Realistic PFA
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Z-pole Event Display
End View Side View
- 2cm x 2cm tile (GLD backup solution) is used in this study.
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Particle Flow Algorithm for GLD
Flow of GLD-PFA
1.Photon Finding 2.Charged Hadron Finding3.Neutral Hadron Finding4.Satellite Hits Finding *Satellite hits = calorimeter hit cell which does not belong
to a cluster core
Note : Monte-Carlo truth information is used for muonand neutrino.
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Photon Likelihood
trkdis velocity meanlay
Edep/nhits chi2
- Five variables are selected to form the photon likelihood function.
Photon
Other
Output
PhotonOther
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Particle Flow Algorithm for GLD
Flow of GLD-PFA
1.Photon Finding 2.Charged Hadron Finding3.Neutral Hadron Finding4.Satellite Hits Finding *Satellite hits = calorimeter hit cell which does not belong
to a cluster core
Note : Monte-Carlo truth information is used for muonand neutrino.
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Charged Hadron Finding- Basic Concept : Extrapolate the charged track and calculate a distance between a calorimeter hit cell and the extrapolated track. Connect the cell that in a certain tube radius (clustering).
Charged TrackCalorimeter input position
Hit Cellsdistance
ECAL
HCAL
- Tube radius for ECAL and HCAL can be changed separately.
- Calculate the distance for any track/calorimeter cell combination.
Extrapolated Track
Tube Radius
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Particle Flow Algorithm for GLD
Flow of GLD-PFA
1.Photon Finding 2.Charged Hadron Finding3.Neutral Hadron Finding4.Satellite Hits Finding *Satellite hits = calorimeter hit cell which does not belong
to a cluster core
Note : Monte-Carlo truth information is used for muonand neutrino.
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Neutral Hadron Likelihood- Four variables are selected to form the NHD likelihood function.
Neutral Hadron
Satellite Hits
velocity Edensity
Edep/nhits meanlayer
Output
Neutral Hadron
Satellite Hits
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e+
e-
Event Display
Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron Z → qqbar @ 91.2GeV
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Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Event Display
Gamma Finding
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Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Event Display
Charged Hadron Finding
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Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Event Display
Satellite Hits Finding
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Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Event Display
Remaining : Neutral Hadron
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- Performance in the EndCap region is remarkably improved recently.- Almost no angular dependence : 31%/√E for |cos|<0.9.
All angle
- Z → uds @ 91.2GeV, tile calorimeter, 2cm x 2cm tile size
Jet Energy Resolution (Z-pole)
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cluster type e photon e chd e nhd Pphoton Pchd PnhdPhoton 93.6 1.88 18.5 87.21 3.57 7.53
CHD 2.44 85.8 12.8 1.31 93.8 3NHD 1.07 3.6 52.8 3.28 22.7 70.7
Satellite 2.86 8.74 15.8 10.20 63.9 24.8
Definition
Efficiency : exxx (total xx E in collected hits)/(true xxx total E in CAL)
Purity : Pxxx (total xxx E in a cluster)/(total E in a cluster)
xxx = Photon, CHD, NHD, Satellite
both e and P values are energy-weighted
Performance
- Energy-weighted Efficiency and Purity
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Jet Energy Resolution
- Jet energy resolution linearly degrades. (Fitting region : |cos|<0.9)
- Energy dependence of jet energy resolution.
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Linearity
- Good linearity. Jet energy can be corrected.
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Zh Study
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Typical Event Display
- ZH → h : Two jets from Higgs can be seen.
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Zh → h @ 350GeV
- Jet energy is corrected by an empirical formula obtained by Z → qqbar studies.- Selection Criteria
- 90 < Evis < 200 GeV - pt >20 GeV/c
Higgs Mass Visible Energy
Missing Mass
- Fast MC• w/o correction• w/ correction
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Kinematical Fit (2jet)- 6 Measured Variables
Jet1 : Ej1, j1, j1
Jet2 : Ej2, j2, j2 (Note : Ej1 > Ej2)- 3 Unmeasured Variables
Z0 : Ez, z, z
- 4 Constraintspj1cosj1sinj1pj2cosj2sinj2pZcosZsinZpj1sinj1sinj1pj2sinj2sinj2pZsinZsinZpj1cosj1pj2cosj2pZcosZEj1 + Ej2 + Ez – Ecm = 0
(Note: jet mass is fixed : pfit = √{Efit2
– (Emeas2 – pmeas
2)} )
→ 1C-fit can be performed.
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Fitted Results (2jet)
Prob > 0.02
- Higgs mass resolution is slightly improved. … But,- Peak at prob=1 indicates the fitting didn’t work well.
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( × Br(h→bb)) Mh (GeV) Mh (MeV)
w/o kinfit 2.04% 117.5 124.8
w/ kinfit 1.89% 119.9 85.6
Fitted Results (2jet)
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Kinematical Fit (4jet)- 12 Measured Variables
Jet1 : Ej1, j1, j1, Jet2 : Ej2, j2, j2 (Higgs pair)
Jet3 : Ej3, j3, j3, Jet4 : Ej4, j4, j4 (Z0 pair) - 5 Constraintspj1cosj1sinj1pj2cosj2sinj2pj3cosj3sinj3pj4cosj4sinj4pj1sinj1sinj1pj2sinj2sinj2pj3sinj3sinj3pj4sinj4sinj4pj1cosj1pj2cosj2pj3cosj3pj4cosj4Ej1 + Ej2 + Ej3 + Ej4 – Ecm = 0Ej3 + Ej4 – √{(pfit,j3
+ pfit,j4) 2 + Mz2} = 0
(Note: jet mass is fixed (OPAL method)pfit = √{Efit
2 – (Emeas
2 – pmeas2)} )
→ 5C-fit can be performed.
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Fitted Results (4jet)
Prob > 0.02
- Higgs mass resolution is slightly improved. … But,- Peak at prob=1 indicates the fitting didn’t work well.
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( × Br(h→bb)) Mh (GeV) Mh (MeV)
w/o kinfit
w/ kinfit
Fitted Results (4jet)
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Summary
• Realistic PFA has been developed using the GEANT-4 based full simulator of the GLD detector.
• Jet energy resolution is studied by using Z->qq events. ILC goal of 30% has been achieved for Z-pole events.
• ZH study based on current PFA performance is now ongoing. Kinematical fitting is employed to get a better performance, but it didn’t work well so far.