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Steven Green, John Marshall, Mark Thomson

Performance at ILC

Performance of PandoraPFA reconstruction for ILC

Performance of PandoraPFA reconstruction for ILC, comparing with perfect pattern recognition. For 50 to 250Gev range the PandoraPFA reconstruction has a resolution < 3.8%. For 60 to 250Gev, it meets the requirement of seperating W and Z bosons.

Resolution of PandoraPFA for various angles and energies

Resolution of PandoraPFA for various angles and energies for ILC. For cos(θ) < 0.95 and energy > 45 GeV, it meets the requirement of seperating W and Z bosons.

For fine granularity particle flow, jet energy resolution needs to be σE/E < 3.5%. This gives the ILC the jet resolution to be able to differentiate W and Z bosons.

Benchmark performance using jet energy resolution in Z decays to light quarks. The total energy is used to avoid complications of jet finding and no backgrounds included.

Current performance, full GEANT4 simulations are shown in the right graph. For the 50 to 250Gev energy region the PandoraPFA reconstruction has a resolution < 3.8%. For the 60 to 250Gev energy region, it meets the requirement of seperating W and Z bosons.

Pandora only has a weak dependence on modelling of hadronic shower, which is < 5% (on the total resolution, not just the hadronic confusion term), suggesting Particle Flow is rather robust to modelling of hadronic showers.

Main performance driver varies with energy:
• High energy jets: confusion
• Low energy jets: energy resolution
• Cross-over between 100 and 120 GeV
• Very high energy: leakage will be important

From that, we optimised detector design by considering:
• B-field
• R : inner radius of ECAL
• L : length, equivalently aspect ratio L/R
• ECAL and HCAL segmentation
• HCAL thickness : number of interaction lengths
• HCAL sampling fraction : ratio of the active to the absorber material thicknesses