Overview of W+HF Analyses
Ford Garberson
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Introduction/Motivation
• Many analyses need good
understanding of W+heavy-flavor
background
– Many analyses working in
different ways
• Impossible to make one-size-fits all
prescription
• But still need to come up with
general guidelines
• Results are very important for
some analyses
– Example: top X-section analysis,
one of largest systematics!
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Lepton + Jets X-Section with b-Tagging
Systematics Table
Approach To Uncertainties
• Base results and uncertainties from measurements in low-jet multiplicity
bins
– Tag-counting analysis (update today)
– SV0 mass fit analysis
• Now being taken over (with modification) by standard model group
• Then project into signal region
– 2-jet bin for single top, 3,4,5-jet bin for ttbar
• Open questions:
– How should we do projection/theory uncertainties
• Report on Alpgen studies by Clemens and Daniel today
• NLO studies will probably be needed to significantly reduce these uncertainties in the
end
– Some studies under way in both top and SM groups
– How will we cooperate with SM group/use their related results?
• Trying to coordinate a meeting with them as soon as possible
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Current Prescriptions
• Currently assuming:
– 1.3 +/- 0.6 for Wbb/Wcc scale factor
• To cover significant difference between two measurements
– 1.0 +/- 0.4 for Wc scale factor
– Driven by measurements before Moriond
– Refinements/bug-fixes since then shown on next
page. Are these numbers still appropriate?
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Latest Measurements
• For SV0 Mass and Tag-Counting Method
– Note: SV0 mass has not been updated in some time using top-group selection
cuts. SM selection cuts lead to a significantly larger asymmetry between 1-jet
and 2-jet bins
Tag-Counting Analysis (Updated numbers today?)
SF:
Wbb/Wcc
Wc
0.84 +/- 0.52
1.45 +/- 0.67
Muon Channel SV0 Mass Analysis: (Electron channel not usable)
W+b:
W+c
And cc:
•
Note: subtracting Wcc leads to SF=1.25 in both the 1 and 2-jet bins
Should update our prescriptions?
– 1.3 +/- 0.6 still looks ok for Wbb to me for top selection … but some studies in SM group
suggest between 2.0-2.5 in 2-jet bin under their selection
– But 1.0 +/- 0.4 for Wc does not look so good any more: results are slightly larger now
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