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e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting PowerPoint Presentation
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e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting

e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting

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e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting

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  1. e⁻ e⁺-> e⁻ e⁺ Energy ResolutionIssues After Last meeting • Select events with 2 tracks only, to remove bremsstrahlungevents • Use energy of the clusters, not the track momentum • Energy resolution for bhabha events is : • ΔE/E ² = 2.3 10¯⁵ => ΔE/E = 3.5 % for 1.5 TeV e± • Why is ΔE # 0.2/√E + 0.01 (CDR) = 1.12 % at 1.5 TeV ? WG6, J-J.Blaising, LAPP/IN2P3

  2. Energy ResolutionEvents without Photons • To understand the e- energy resolution: Select events without FSR and Bremssthalung (using the generator and simulation status bits), 9500 events left. • These events should not contain photons, but ~ 2/3 have γs. • The γs are created by Pandora which breaks e± into e± and nγ (known feature). • Is not an issue; the analysis software recombines them. • In the events left, 90% contain PFOs which are neutrons. • When these events are removed only ~ 300 events are left and ΔE/E²=5.110¯⁶ • But mean value off by 3%. WG6, J-J.Blaising, LAPP/IN2P3

  3. Energy ResolutionEvents without Photons • Apply event/event correction x0.97 • => ΔE/E²=9.7 10¯⁶ • ΔE/E= 1.5 % for 1.5 Tev e± • Close to the expected value ΔE/E=1.12 % WG6, J-J.Blaising, LAPP/IN2P3

  4. Energy ResolutionEvents with Photons and Neutrons • Force software to consider neutrons as photons • => ΔE/E² =1.25 10¯⁵. • but the mean value is off by 3%. • Apply global E correction • ΔE/E² =1.18 10¯⁵ • ΔE/E = 1.8% for 1.5 TeV e± • This is ~ a factor two better wr. to last meeting and closer tothe expected resolution 1.12 % (CDR) • The right treatment of the neutral energy deposit in the HCAL, may improve the resolution further. WG6, J-J.Blaising, LAPP/IN2P3

  5. ΔE/E ΔE/E as a function of E: For 500 GeV < E > 1500 GeV: ΔE/E=0.38/√E+ 0.01 Expected ΔE/E=0.2/√E+0.01 WG6, J-J.Blaising, LAPP/IN2P3

  6. Photons ΔE/E Use Mokka gun to simulate γs at θ=30⁰, smeared over φ, Eγ=200, 400, 600,800, 1000 GeV After reconstruction, remove events with photon conversion, for each file of 2000 events ~ 1300 events are left. Remove events with Neutrons, 90% left at 200 GeV, 50% at 400 GeV ΔE/E=1.9% at 200 GeV and 1.6% at 400 GeV, but mean shifted WG6, J-J.Blaising, LAPP/IN2P3

  7. Photons ΔE/E 15% left at 600 GeV, 12% at 800 GeV ΔE/E=1.4% at 600 GeV and 1.4% at 800 GeV, mean shift increases with energy of γ WG6, J-J.Blaising, LAPP/IN2P3

  8. Photons ΔE/E For γ events without neutrons the energy resolution ~ ok , but he mean value of ΔE/E is off; the offset increases with Eγ The number of events with neutrons increases with Eγ; why ? For e± events the mean of ΔE/E² is off ~ 3% WG6, J-J.Blaising, LAPP/IN2P3

  9. Backup WG6, J-J.Blaising, LAPP/IN2P3

  10. √s’ WG6, J-J.Blaising, LAPP/IN2P3

  11. √s’ WG6, J-J.Blaising, LAPP/IN2P3