1. LPC Jet/Met meeting 1/12/2006L. Perera1 Jet/Calorimeter Cluster Energy Corrections – Status Goal: To improve the individual jet energy determination based on measured cluster structure. Response of the ECAL is different for EM particles (photons/ electrons) and hadrons. Energy determination will improve if we can separate EM particles and hadrons and apply separate corrections.

2. LPC Jet/Met meeting 1/12/2006L. Perera2 Classification –EM particles: Energy in ECAL should be okay as it is calibrated for electrons. –Non-interaction hadrons: All energy (except MIP), in HCAL and it is calibrated for hadrons (charged pions). –Interacting hadrons: deposit some energy in ECAL- needs to be corrected. Challenge: Overlapping particles (many particles going through the same cell)

3. LPC Jet/Met meeting 1/12/2006L. Perera3 Procedure Cluster cells in the ECAL and HCAL Match ECAL and HCAL clusters and find the fraction of ECAL energy ( f ) in the matched clusters : f= E/(E+H) Classification: 0.95 < f < 1 EM particle 0.1 < f < 0.95 Interacting hadron 0 < f < 0.1 non-interacting (MIP) hadrion energy in ECAL+ HCAL and ECAL energy > MIP interacting hadron also works

4. LPC Jet/Met meeting 1/12/2006L. Perera4 Analysis Using a 120 GeV Z´  q q (u,d,s) MC sample ( no noise or pile-up) Analysis done in ExRootAnalys Currently considering ECAL /HCAL barrel A simple algorithm to cluster ECAL and HCAL cells separately in eta-phi: –Seed cell E T >0.5 GeV –Add neighboring (3x3) cells (dR< 0.03 for ECAL, dR<0.15 for HCAL) –Mark out used cells Match ECAL and HCAL clusters (dR <0.15)

5. LPC Jet/Met meeting 1/12/2006L. Perera5 EB cluster HB cluster + pion + proton + photon Jet

6. LPC Jet/Met meeting 1/12/2006L. Perera6 number of GenJets pT >10GEV GenJet  Number of RecJets RecJet 

7. LPC Jet/Met meeting 1/12/2006L. Perera7 jet energy in charged hadrons (  K p) 12 Energy in all charged hadrons within a cone of 0.5 around GEnJet axis (as a fraction of GenJet energy) At the IP After propagating them to HCAL in 4T.

8. LPC Jet/Met meeting 1/12/2006L. Perera8 RecJet GenJet comparison RecJet has 60% of the energyDijet mass form RecJet is 70% of from GenJet

9. LPC Jet/Met meeting 1/12/2006L. Perera9 ECAL/HCAL Cluster matching ( R<0.15 ) within a jet outside the jets

10. LPC Jet/Met meeting 1/12/2006L. Perera10 Energy distribution in clusters 35% of jet energy is in uniquely matched clusters One ECAL cluster matching one HCAL cluster Easier to do energy correction 30 of jet energy is in clusters which have multiple matches Energy correction is not straightforward

11. LPC Jet/Met meeting 1/12/2006L. Perera11 Cluster Energy Correction estimate the energy correction from a simple fit to test beam data (for now) Use ECAL+HCAL energy of unique match clusters as particle energy

12. LPC Jet/Met meeting 1/12/2006L. Perera12 energy correction Jet energy Correction: 4.5 % increase in jet energy

13. LPC Jet/Met meeting 1/12/2006L. Perera13 Improvement in DiJet mass Mean of dijet mass increased by 4.5% Width of the dijet mass decreased by 6.5% Small but in the right direction !

14. LPC Jet/Met meeting 1/12/2006L. Perera14 ECAL thresholds are too high (ECAL noise 40 MeV) Significance of the improvement of resolution is less when ECAL thresholds are lowerd (100 MeV)

15. LPC Jet/Met meeting 1/12/2006L. Perera15 dR pion photons within Jet dR pi/photon dR pion Jet axis dR pi/photon

16. LPC Jet/Met meeting 1/12/2006L. Perera16 Dijet mass from genJets Z’ mass 3

17. LPC Jet/Met meeting 1/12/2006L. Perera17 DiJet mass after propagating Particles to ECAL pT of pions within Jet

18. LPC Jet/Met meeting 1/12/2006L. Perera18 After rescaling pion energies by distribution in page 11 Dijet mass from RecJets

19. LPC Jet/Met meeting 1/12/2006L. Perera19 Charged hadrons photons Neutral Hadrons (n, K_L) Contribution to Jet Energy

20. LPC Jet/Met meeting 1/12/2006L. Perera20     Pion and ECAL cluster matching photon and ECAL cluster matching

21. LPC Jet/Met meeting 1/12/2006L. Perera21 There seems to be a non linearity in ECAL at low energies ECAL cluster energy/photon energy Photon energy GeV

22. LPC Jet/Met meeting 1/12/2006L. Perera22 Most of photons in the jet are in this region Cause under investigation: seems to be in digitization