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Various progress in Z µ + µ -. EWK Dilepton meeting, 23.11.2010 Arie Bodek, Yeonsei Chung, Jiyeon Han Rochester University Alessio Bonato, Andrei Gritsan, Zijin Guo, Nhan Tran* Johns Hopkins University. Outline. A first look at MC and Data in CMS Features, comparison, implications - PowerPoint PPT Presentation
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Various progress in Zµ+µ-
EWK Dilepton meeting, 23.11.2010
Arie Bodek, Yeonsei Chung, Jiyeon Han Rochester University
Alessio Bonato, Andrei Gritsan, Zijin Guo, Nhan Tran*
Johns Hopkins University
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Outline
• A first look at MC and Data in CMS• Features, comparison, implications
• Implications for analyses of Afb and sin2W• Plans and progress in Afb with event weighting
http://indico.cern.ch/conferenceDisplay.py?confId=112949 (N.T.)
• Plans and progress in sin2W with likelihood methodhttp://indico.cern.ch/conferenceDisplay.py?confId=113453 (A.
Gritsan)
A report on various activities related to Zµ+µ-
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Data/MC: Kinematic distributions
MC: /DYToMuMu_M-20_CT10_TuneZ2_7TeV-powheg-pythia/Fall10-START38_V12-v1
data: 35 pb-1
Basic plots match those shown elsewhere with reasonable agreement
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More MC plots
Interesting acceptance effect
resolutionresolution vs. eta
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Afb in MC
Full Y range 1 < |Y| < 2
Effect seen last time…
Forward-backward asymmetry switches sign near Z peakMore severe at greater Y
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Resolution and binningLet’s look at one specific mass bin…
Resolution with right-side tail, “artificial” due to binning
Reason for Afb sign flip
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Implications for event weighting Afb
• Resolution/FSR and bin migration effects large (could increase bin size)
• Solution: need to account for by including in weighting tables; FSR and “fast smear” at generator level, need to implement negative weighting
raw Afb
Event weighting for
dilution
weighted Afb
Pull corrections for
detector effects
measured Afb
raw Afb
Event weighting for dilution,
FSR, resolution
weighted Afb
Pull corrections for
remaining effects
measured Afb
Reminder of the strategy:
Change strategy:
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ResolutionResolution effects need to be understood for both likelihood technique (resolution convolution) and event weighting technique
(fast smear for weighting)
Fit with double Gaussian for both m and m2
resolution - technical reasons due to analytical convolution in likelihood
approach
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AcceptanceFlat acceptance not a good model, lose events
at larger Gen level (flat acceptance, ||<2.1), Reco level (||<2.1)
Parametrize acceptance with polynomial fit (acceptance function)
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Implication for likelihood analysis
• Recall, likelihood function over 3 observables (m,Y,cos) used in angular analysis and fitting of Weinberg angle, sin2W.
• Analytical description involving• Parton-level cross-section• Parton distribution functions• Dilution• Acceptance - flat acceptance• Resolution - Gaussian smearing (No FSR)
• Implement more realistic modeling of detector effects using MC for acceptance and resolution
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Resolution and acceptance
1D projections with flat acceptance and Gaussian smearing
Now, implementing realistic resolution and acceptance
*Fit under study
Y mcos
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