1. PFA Study with Jupiter Contents : 1. Introduction 2. GLD-PFA
3. Z->qqbar Study
4. Zh Study
5. Summary
FJPPL KEK
September 29th, 2006
Tamaki Yoshioka
ICEPP, Univ. of Tokyo
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2. Introduction → Jet energy resolution is the key in the ILC physics.
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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3. Geometry in Jupiter Solenoid TPC Hadron Calorimeter (HCAL) VTX, IT
Muon Detector
Electromagnetic Calorimeter (ECAL)
Dodecagonal Shape
As of August 06
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4. Calorimeter Geometry in Jupiter
Readout Line =10cm
349.4cm
BarrelHD
229.8cm
BarrelEM
210cm
270cm
EndcapHD
Barrel.InnerRadius=210cm
EndcapEM
Endcap.InnerRadius=40cm IP
Barrel.HalfZ=280cm
419.4cm
280cm
299.8cm
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5. Calorimeter Structure
Active Layer
Absorber
Current cell size :
2x2cm
Can be changed.
ECAL
W/Scinti./Gap
3/2/1 (mm) x 33 layers
HCAL
Fe/Scinti./Gap
20/5/1 (mm) x 46 layers
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6. GLD-PFA
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7. Particle Flow Algorithm for GLD
Flow of GLD-PFA
Photon Finding
Charged Hadron Finding
Neutral Hadron Finding
Satellite Hits Finding
*Satellite hits = calorimeter hit cell which does not belong
to a cluster core
Note : Monte-Carlo truth information is used for muon
and neutrino.
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8. Photon Likelihood (Input)
- Five variables are selected to form the photon likelihood function.
trkdis
velocity
meanlay
Edep/nhits
chi2
Photon
Other
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9. Photon Likelihood (Output)
linear
Cut position is set
to be 0.7.
Other
Photon
log
Photon
Other
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10. 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).
Extrapolated Track
Calculate the distance
for any track/calorimeter
cell combination.
HCAL
Tube Radius
Hit Cells
Tube radius for ECAL
and HCAL can be changed
separately.
distance
ECAL
Calorimeter input position
Charged Track
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11. Neutral Hadron Likelihood (Input)
- Four variables are selected to form the NHD likelihood function.
velocity
Edensity
Edep/nhits
meanlayer
Neutral Hadron
Satellite Hits
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12. Neutral Hadron Likelihood (Output)
linear
Satellite
Hits
Neutral
Hadron
Cut position is set
to be 0.73.
log
Neutral Hadron
Satellite Hits
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13. Z -> qqbar
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14. Z-pole Event Display End View Side View
- 2cm x 2cm tile (GLD backup solution) is used in this study.
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15. Event Display e+ e- Z → qqbar @ 91.2GeV Next: 電子、陽電子衝突 Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Z → 91.2GeV
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Next: 電子、陽電子衝突

16. Event Display Gamma Finding Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Gamma Finding
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17. Event Display Charged Hadron Finding Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Charged Hadron Finding
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18. Event Display Satellite Hits Finding Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Satellite Hits Finding
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19. Event Display Remaining : Neutral Hadron Yellow : Photon
Red, Green : Charged Hadron
Black, Blue : Neutral Hadron
Remaining : Neutral Hadron
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20. Performance - Energy-weighted Efficiency and Purity Definition
Efficiency : xxx  (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  and P values are energy-weighted
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21. Jet Energy Resolution
- Z → 91.2GeV, new calorimeter geometry, 2cm x 2cm tile
In barrel region, ILC goal of 30% has been achieved.
Performance in 0.7<|cosθ|<0.8 is too bad. → Already fixed.
All angle
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22. Energy Dependence - Energy dependence of jet energy resolution.
Bad performance for higher energy.
Not so bad performance for < 100 GeV Jet.
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23. Linearity - Good linearity. Jet energy can be corrected. 9/29/2006
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24. Zh → nn h First look at the Zh events with Jupiter and realistic PFA.
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25. Typical Event Display Two jets from Higgs can be seen. 9/29/2006
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26. Zh → nn h @ 350GeV - Fast MC • w/o correction • w/ correction
Higgs Mass
Visible Energy
- Jet energy is corrected by an empirical
formula obtained by Z → qqbar studies.
- Selection Criteria
90 < Evis < 200 GeV
pt >20 GeV/c
Missing Mass
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27. Kinematical Fit - 6 Measured Variables Jet1 : Ej1, qj1, jj1
Jet2 : Ej2, qj2, jj2 (Note : Ej1 > Ej2)
- 3 Unmeasured Variables
Z0 : Ez, qz, jz
4 Constraints
pj1cosjj1sinqj1 + pj2cosjj2sinqj2 + pZcosjZsinqZ = 0
pj1sinjj1sinqj1 + pj2sinjj2sinqj2 + pZsinjZsinqZ = 0
pj1cosqj1 + pj2cosqj2 + pZcosqZ = 0
Ej1 + Ej2 + Ez – Ecm = 0
(Note: jet mass is fixed : pfit = √{Efit2 – (Emeas2 – pmeas2)} )
→ 1C-fit can be performed.
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28. Fitted Results Very Preliminary Prob > 0.02
Higgs mass resolution is significantly improved. … But,
Peak at prob=1 indicates the fitting didn’t work well.
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29. Stretch Functions Too Narrow Strange = Overestimated
The stretch function should form a normal Gaussian if the X and
s are proper.
Too Narrow
= Overestimated
Strange
Need to
understand.
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30. 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.
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