1. Short Overview on calibration
Jet calibration as it is now
What we correct and how
Latest news on default calibration from F.Paige
step to final comparison of existing schemes
Future steps
May 4th, 2006
Hadron Calibration - Munich
C.Roda

2. What we mean for calibration…
Reconstructed Jet (with cone, or KT)
MC particle Jet (with cone, or KT)
Reconstruction
We apply the calibration algorithm to take the scale of the Reconstructed jet from the EM scale to the to the MC jet scale (compensation).
Parton Jet
invertire : a dx rico a sx gen
May 4th, 2006
Hadron Calibration - Munich
C.Roda

3. EM Scale Difference from 1 is due to: e/h non compensation
Energy lost in dead material
B field effect
Jet clustering effects
A.Gupta
May 4th, 2006
Hadron Calibration - Munich
C.Roda

4. Size of contribution from various effects
Results from Atlfast: comparison of Erec/Emc
P.Francavilla I.Vivarelli
May 4th, 2006
Hadron Calibration - Munich
C.Roda

5. Size of contribution of various effects
Results from Atlfast
P.Francavilla I.Vivarelli
May 4th, 2006
Hadron Calibration - Munich
C.Roda

6. Present flow of Jet Calibration
EM Scale, noise suppresion
EM Scale, more noise suppresion
CaloCells
CaloTowers / TopoClusters
Cone, Kt algorithm
Calibration scheme
Calibrated Jets to MC energy
Uncalibrated Jets
In situ calibration, underlying, pileup, out of cone …
Calibrated Jets
May 4th, 2006
Hadron Calibration - Munich
C.Roda

7. Use global jet scale, See A.Dotti presentation, (Pisa groups)
Calibration scheme
Energy resolution minimization (with linearity constraint) to obtain weights W():
W(Jet Energy) x Sample energy
W(Cell Energy density) x Cell energy
W(Cell Energy, Jet Energy) x Cell energy
All weights are also function of eta.
Different functions are assumed to describe the
weight energy dependence.
Simple and fast but less performant, useable at trigger level ? (A.Gupta)
Default in Athena, used in all physics analysis up to now and for ETMiss. Indicated with H1 (F.Paige)
Use global jet scale, See A.Dotti presentation, (Pisa groups)
May 4th, 2006
Hadron Calibration - Munich
C.Roda

8. F.Paige/H1 Method - defaults
Linearity,Resolution
F.Paige/H1 Method - defaults
||<0.7
May 4th, 2006
Hadron Calibration - Munich
C.Roda

9. ETfinal = ETcal x F(, Etcal) for  = 0.5 bins
0 < || < 0.5
Etrec/ETMc
ETfinal = ETcal x F(, Etcal) for  = 0.5 bins
This is all done calculated on dijet samples for different je algorithms.
May 4th, 2006
Hadron Calibration - Munich
C.Roda

10. Correction functions F(Et,eta)
Given a sufficient fine binning in eta and Et it is clear that linearity is restored. No improve on the resolution is espected. The real test is to see if linearity is restored on a different sample.
Check on SU3 sample: quark rather than gluon jets and Herwig instead of Pythia.
May 4th, 2006
Hadron Calibration - Munich
C.Roda

11. Before applying correction function After applying correction function
May 4th, 2006
Hadron Calibration - Munich
C.Roda

12. SU3 Cone R = 0.4 CaloTowerJets
May 4th, 2006
Hadron Calibration - Munich
C.Roda

13. SU3 Cone R = 0.4 CaloTowerJets
May 4th, 2006
Hadron Calibration - Munich
C.Roda

14. Comparison of different methods
Pisa method
F.Paige/H1 method
A.Gupta
The three calibration methods are in Athena. All parameters obtained on Rome samples. More results on Pisa calibration will be shown by Andrea in the next presentation. The framework to do the comparison in a consistent manner is in place. Final results on comparison by Barcellona.
May 4th, 2006
Hadron Calibration - Munich
C.Roda

15. Next steps
Need to better understand the calibration method for the low energy (ET<30 GeV) jets.
Understand degradation of energy resolution with respect to TDR
Noise treatment: noise is suppressed using different tools. However a detailed study of noise suppression algorithms and performance is still missing. In the official production we have requested a few dijet events without noise. This can be used as the reference events to finalize this study.
Weak point of all chi**2 minimization: the method to obtain the weights is not authomatic and need human iterations. Ambreesh has started to implement in Athena the framework to have this done in more authomatic way however the framework needs test from users.
Detailed comparison of three schemes with standard macros.
Robusteness of the method: apply to real data, CTB pions – see I.Vivarelli presentation for very preliminary results.
Assess performance of calbration when pile-up is used
Start assessing integration between jet and had calibration.
May 4th, 2006
Hadron Calibration - Munich
C.Roda

16. May 4th, 2006
Hadron Calibration - Munich
C.Roda

17. May 4th, 2006
Hadron Calibration - Munich
C.Roda

18. Comparing different schemes
CaloTowerNoise
EME
3 sigma asym
EMB
CaloTopoCluster
Plots show how much negative enegy is left in jets after noise subtraction algorithm is applied in each calorimeter region.
TileBarrel
TileExB
HadLar FW
CaloTopoCluster < 3 sigma sym < CaloTowerNoise
Check what are the conclustion on Ambreesh note
Gap
May 4th, 2006
Hadron Calibration - Munich
C.Roda