e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting
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e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting 24 July 2012 WG6, J-J.Blaising, LAPP/IN2P3 1 • Select events with 2 tracks only, to remove bremsstrahlung events • 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 ?
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e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting. Select events with 2 tracks only, to remove bremsstrahlung events Use energy of the clusters, not the track momentum E nergy resolution for bhabha events is : Δ E/E ² = 2.3 10¯⁵ => Δ E/E = 3.5 % for 1.5 TeV e± - PowerPoint PPT Presentation
Transcript of e⁻ e⁺-> e⁻ e⁺ Energy Resolution Issues After Last meeting
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e⁻ e⁺-> e⁻ e⁺ Energy ResolutionIssues After Last meeting
24 July 2012 WG6, J-J.Blaising, LAPP/IN2P3
• Select events with 2 tracks only, to remove bremsstrahlung events • 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 ?
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Energy ResolutionEvents without Photons
24 July 2012 WG6, J-J.Blaising, LAPP/IN2P3
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 =5.1 10¯⁶But mean value off by 3%.
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Energy ResolutionEvents without Photons
24 July 2012 WG6, J-J.Blaising, LAPP/IN2P3
Apply event/event correction x0.97 => ΔE/E² =9.7 10¯⁶ÞΔE/E= 1.5 % for 1.5 Tev e±Close to the expected value ΔE/E=1.12 %
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Energy ResolutionEvents with Photons and Neutrons
24 July 2012 WG6, J-J.Blaising, LAPP/IN2P3
Force software to consider neutrons as photons => ΔE/E² =1.25 10¯⁵.but the mean value is off by 3%. Apply global E correctionÞ ΔE/E² =1.18 10¯⁵Þ ΔE/E = 1.8% for 1.5 TeV e±
This is ~ a factor two better wr. to last meeting and closer to the expected resolution 1.12 % (CDR)
The right treatment of the neutral energy deposit in the HCAL, may improve the resolution further.
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ΔE/E
24 July 2012
ΔE/E as a function of E:For 500 GeV < E > 1500 GeV: ΔE/E=0.38/√E+ 0.01Expected ΔE/E=0.2/√E+0.01
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Photons ΔE/E
24 July 2012
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 GeVΔE/E=1.9% at 200 GeV and 1.6% at 400 GeV, but mean shifted
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Photons ΔE/E
24 July 2012
15% left at 600 GeV, 12% at 800 GeVΔE/E=1.4% at 600 GeV and 1.4% at 800 GeV, mean shift increases with energy of γ
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Photons ΔE/E
24 July 2012
For γ events without neutrons the energy resolution ~ ok , but he mean value of ΔE/E is off; the offset increases with EγThe number of events with neutrons increases with Eγ ; why ?For e± events the mean of ΔE/E² is off ~ 3%
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Backup
24 July 2012
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√s’
24 July 2012
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√s’
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