Dimuons and virtuality

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Di-muons and virtuality

• A. Koutsman
• ATLAS-NIKHEF Workshop
• 9-11 may 2006

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Supersymmetry

• Best motivated extension
• Solves hierarchy problem (divergence scalar
  fields, SM Higgs)
• Solves naturalness problem (fine-tuning problem)
• Gives a credible cold dark matter candidate
  (R-parity)
• Required by string theory (not necessarily at TeV
  scale)

• Extension of SM Qbosongt fermiongt,
  Qfermiongt bosongt
• Complexifies SM Higgs Sector 2 complex Higgs
  doublets (and appropriate SUSY partners)
• At least 105 new parameters in addition to SM
  (MSSM)

3
mSUGRA

• SUSY is broken via hidden sector
• In SUGRA models gravity communicates the breaking
• Five(!) parameters to define an mSUGRA model
• m0 common mass of scalars at GUT scale
• m1/2 common mass of gauginos and Higgsinos at
  GUT scale
• A0 common value of trilinear couplings at GUT
  scale
• tanß ratio of Higgs vacuum expectation values
• sign µ 1 µ SUSY conserving Higgs mass
• Six points chosen in mSUGRA parameter space by
  ATLAS
• Lightest supersymmetric particle (LSP)
  (neutralino)

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SUSY production at LHC

• At LHC squarks and gluinos production dominates,
  which subsequently decay through chains to the LSP

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dilepton decays
via slepton
via chargino
via Z/Higgs
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Alex mSUGRA point

• PYTHIA (Following Wiki example)
• m0 200
• m1/2 250
• A0 100
• tanß 10
• sign µ

183.92 GeV 98.14 GeV 183.42 GeV 112.48
GeV 219.24 GeV
85.7 GeV
h
http//kraml.home.cern.ch/kraml/comparison/
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Alex mSUGRA pointselection cuts
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Alex mSUGRA point
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Alex mSUGRA point
Rest frame of
LSP always real !!!
Z virtual Why such a sharp peak? What is all the
grass? (Not IS/FS radiation)
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Alex mSUGRA point
No direction correlation between muons GRASS
Breit-Wigner with a kinematic cut-off SHARP PEAK
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BACK UP SLIDES
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ATLAS mSUGRA point 3

• PYTHIA
• m0 200 (200)
• m1/2 100 (250)
• A0 0 (100)
• tanß 2 (10)
• sign µ - ()

http//kraml.home.cern.ch/kraml/comparison/
97 GeV 45 GeV 96 GeV 69 GeV 207 GeV
52 GeV
h
Values from Technical Design Report, PYTHIA
generates somewhat different masses
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ATLAS mSUGRA point 3
TDR
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ATLAS mSUGRA point 3
Rest frame of
LSP always real !!!
Why is there such a difference between point 3
and our point??? Also ATLAS TDR Point 5
reproduced with succes by Paul
Z virtual Z produced as real as possible But
where is the sharp peak?
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Ongoing work Suggestions welcome
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No Selection cuts except missing ET
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pT
Missing ET gt20 GeV
Missing ET gt20 GeV gt1 good reco muon mother
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Angle between muons in rest-frame
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Supersymmetry