Performance and Sensitivity of H.E.S.S. Christopher van Eldik Max-Planck-Institut für Kernphysik Heidelberg 2006 Philippe Plailly. www.eurelios.com PSF & FoV Cut Efficiencies Energy Estimation Flux Sensitivity CTA Meeting Berlin May 4-5, 2006
PSF & FoV
Optical Point Spread Function stiff mirror dish design - no need for active mirror control - slewing speed still 100 /min. opsfs match expectations - agree with simulations - all 4 telescopes similar ½ H.E.S.S. pixel size opsfs stable over two years - typical broadening 1-5 % / yr - just needs monitoring
Angular Resolution about 0.1 per event significantly improves - with image size (hard cuts) - with telescope multiplicity moderately decreases - with zenith angle Offset 0 Γ = 2.0
Angular Resolution about 0.1 per event significantly improves Offset 0 Γ = 2.0 - with image size (hard cuts) - with telescope multiplicity moderately decreases - with zenith angle Γ = 2.0 good resolution even for large offsets in camera important for extended sources
Off-Axis Sensitivity good off-axis performance - for extended sources - for surveys Crab Nebula still ~70% relative rate at 1.5 offset very good agreement with simulations
Cut Efficiencies
percentage Cut Efficiencies hard cuts 0.5 offset zenith angle (deg) Preselection: - image size > 200 p.e. - nominal distance < 2 - at least 2 telescopes
percentage Cut Efficiencies hard cuts 0.5 offset zenith angle (deg) Preselection: - image size > 200 p.e. - nominal distance < 2 - at least 2 telescopes Image Shape: - keeps > 80% of γ's - background reduction by factor 40 (total: 250)
percentage Cut Efficiencies hard cuts 0.5 offset zenith angle (deg) Preselection: - image size > 200 p.e. - nominal distance < 2 - at least 2 telescopes Image Shape: - keeps > 80% of γ's - background reduction by factor 40 (total: 250) Reconstructed Direction: - point source cut (0.11 )2 - keeps 75% of γ's - reduces background by factor 400 (total: 100.000)
Cut Efficiencies Quality factor Q = / CR hard cuts 0.5 offset standard cuts 0.5 offset excellent background suppression - already before θ2 cut very good γ-ray efficiency - somewhat worse at very large zenith angles
Energy Estimation
Energy Resolution std std energy resolution ~15% almost no dependence on zenith angle no dependence on off-axis angle no significant energy bias std
Energy Resolution std std energy resolution ~15% almost no dependence on zenith angle no dependence on off-axis angle no significant energy bias safe energy threshold: energy bias < 10% std
Energy Threshold = peak of differential rate 100 GeV at zenith before cuts reached design goals
Flux Sensitivity
Flux Sensitivity MAGIC I ICRC 2005 HESS I (predicted)) HESS I (achieved) crab-like spectrum hard cuts sensitivity as predicted - even slightly better at small energies
Summary H.E.S.S. combines - very good angular resolution - good acceptance across FoV - excellent hadron rejection - good energy resolution GEO 06/2005 Design goals met Alternative analysis strategies show even better performance in some aspects
Backups
Cut Efficiencies Off-data match MC protons background-subtracted signal from Crab matches MC gammas