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Jet/Calorimeter Cluster Energy Corrections – Status

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.

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Jet/Calorimeter Cluster Energy Corrections – Status

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  1. 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. L. Perera

  2. 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) L. Perera

  3. 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 L. Perera

  4. 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 ET>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) L. Perera

  5. EB cluster + pion + proton + photon HB cluster Jet L. Perera

  6. number of GenJets pT >10GEV GenJet h h Number of RecJets RecJet h L. Perera

  7. jet energy in charged hadrons (p K p) 1 2 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. L. Perera

  8. RecJet GenJet comparison RecJet has 60% of the energy Dijet mass form RecJet is 70% of from GenJet L. Perera

  9. ECAL/HCAL Cluster matching (DR<0.15) within a jet outside the jets L. Perera

  10. 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 L. Perera

  11. 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 L. Perera

  12. energy correction Jet energy Correction: 4.5 % increase in jet energy L. Perera

  13. 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 ! L. Perera

  14. ECAL thresholds are too high (ECAL noise 40 MeV) • Significance of the improvement of resolution is less when ECAL thresholds are lowerd (100 MeV) L. Perera

  15. dR pion Jet axis dR pi/photon dR pi/photon dR pi/photon dR pion photons within Jet L. Perera

  16. Dijet mass from genJets Z’ mass 3 L. Perera

  17. DiJet mass after propagating Particles to ECAL pT of pions within Jet L. Perera

  18. After rescaling pion energies by distribution in page 11 Dijet mass from RecJets L. Perera

  19. Charged hadrons photons Neutral Hadrons (n, K_L) Contribution to Jet Energy L. Perera

  20. Df Df Dh Dh photon and ECAL cluster matching Pion and ECAL cluster matching L. Perera

  21. Photon energy GeV ECAL cluster energy/photon energy There seems to be a non linearity in ECAL at low energies L. Perera

  22. Most of photons in the jet are in this region Cause under investigation: seems to be in digitization L. Perera

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