Few activities in Statistics: Higgs Exotics

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Few activities in StatisticsHiggs Exotics
Samir FERRAG University of Glasgow
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Introduction

• Very useful Stat Workshop at CERN last week
• Interacted and triggered some projects
• Alex Read (Shape analysis for ttH, Saverio)
• Kyle (Stat Framework for ATLAS based on Roofit)
• Feasibility of ttH
• Extract the constraints on the background
  uncertainty
• If feasible define the priorities on real data
• PDF, Background, ttH
• Counting experiment constraints to be extended to
  shape analysis

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Theoretical uncertainties on ttbb
Quadratic summation
High-x gluons are not the main Source of
uncertainties 3
Relative uncertainty ()
PDF number

• ttbb production via gluon-gluon and
  quark-antiquark fusions
• ttbb cross section from AlgGen sttbb 2.55 pb
• Theoretical uncertainties
• /- 6 from PDFs (classical recipe)
• /- 55 from factorisation and
  renormalisation scales 1/2m0 ltmlt2m0
• PDF uncetainties can be irreducible and
  constitutes a serious source to
• constraint the analysis

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constraint on ttH

• For a relative systematic uncertainty e on the
  background, the significance is

• By extracting the relation between S/B and e, we
  obtain the constraint relation

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Constraint on ttH for 10fb-1

• Higgs mass120GeV

S/B
5s
4s
Requested S/B For 3s significane For 6 PDF
uncertainty
3s
2s
S/B0.14 From Markus analysis (ATLFAST)
systematic uncertainty on B ()
6 of PDF uncertainties (on ttbbttjj)
Need 1 to 2 of accuracy On background to reach
2s significance
6
Constraint on ttH for 100fb-1

• Higgs mass120GeV

S/B
5s
4s
3s
Requested S/B For 3s significane For 6 PDF
uncertainty
2s
S/B0.14 From Markus analysis (ATLFAST)
systematic uncertainty on B ()
6 of PDF uncertainties
Need 4 of accuracy On background to reach 3s
significance
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Variation with the Higgs mass

• Higgs mass120GeV

• Higgs mass130GeV

• 10 fb-1

ATLFAST analysis

• 100 fb-1

ATLFAST analysis
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Conclusion Counting experiment!

• Is ttH feasible ?
• Reduce the PDF uncertainties to ltlt 6
• if not
• PDF uncertainties are enough to cancel the
  discovery power
• Background (ttbbttjj) measurement accuracy at lt
  5
• Including PDF uncertainties above (?)
• Systematic uncertainties from Luminosity (?)
• Reconstruction and performance tools (?)
• If Likelihood, Probability Density Function
  parameterisation (?)
• For 100fb-1 (in 2011) and Background accuracy of
  5
• S/B30 for a 5s discovery (mHiggs120 GeV)
• S/B16 for a 3s evidence (mHiggs120 GeV)

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Extend to Shape Analysis
From the Statistic workshop at CERN
Counting Experiment
Shape (PDF)
Alex Read Saverio ? Chris
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First Steps in Roofit

• Roofit part of the package ROOT 5-02
• Compiled and installed on my Laptop
• Goal use it and develop the framework for
• Compute limits (Exotics)
• Research of bumps (Higgs)
• Very nice Topic for Glasgow/UK collaboration