UCLA

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Top Properties at Tevatron Run II 2008
QCD Conference
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Charles Plager UCLA For the CDF and DØ
Collaborations
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New Era of Top Precision Physics!

• CDF and DØ now have more than thirty (30 !!!)
  times as much integrated luminosity as we did
  when we discovered the top quark in Run I!
• With the data we have recorded, we are now able
  to have large, very pure top samples.
• For example, of the almost 50 results that CDF
  sent to the winter conferences, more than half
  were in top physics!

Double B-Tag W Jets Candidates
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Top Quark Review

• Fundamental question
• Is it the truth, the Standard Model (SM) truth,
  and nothing but the truth?
• Did we really find the top quark?
• Is it the SM top quark?
• Is it only the SM top quark?
• The top quark is an ideal place to look for
  Beyond the Standard Model Physics!

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tt Pair Lepton Jets Decay
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What Can We Study About Top Quarks?
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Top physics is very rich.
Branching ratios Rare decays Non-SM decays Decay
kinematics W helicity Vtb
Production cross section Production
mechanism Resonance production Production
kinematics Spin polarization
Top charge Top spin Top mass Top width
In todays talk.
Public Tevatron analyses.
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Top Pair Decay Modes

• According to the SM, top quarks almost (?) always
  decay to Wb.
• When classifying the decay modes, we use the W
  decay modes
• Leptonic
• Light leptons (e or ?)
• Tauonic (?)
• Hadrons

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Search for tt Resonances
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• Uses lepton jets
• event selection
• B-tag.
• Invariant mass
• reconstruction
• Assume p?T MET
• Solve for P?z assuming W mass.
• Allows for events with less than three jets.

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Search for tt Resonances, cont.
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• For Z limits, assuming a lepto-phobic Z
• Br (Z ! tt) 100
• MZ gt 760 GeV

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Worlds Most Precise Measurement!
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Search for Invisible Top Decays

• What do we mean by invisible?
• Not (well) reconstructed as double b-tag lepton
  jets.
• What would happen if there were a large branching
  fraction to an invisible decay? For example,
• Br (t ! Invisible) 10?
• Br (t ! Wb) 90
• P (tt ! Wb Wb) 81
• ) For a purely invisible decay, we should have
  an 19 deficit when we look at the L J event
  yield for a given theoretical cross section.

XY
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Feldman-Cousins Acceptance Bands
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Search for Invisible Top Decays, cont.

• From Cacciari et al. (hep-ph 0804.2800)
  assuming CTEQ PDFs.

Worlds First Measurement!
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Search for the Top FCNC Decay t ? Zq

• Top FCNC extremely rare in the SM B(t ? Zq)
  O(1014)
• Beyond SM B(t ? Zq) up to O(104),
• Any signal at Tevatron or LHC New Physics.
• Signature tt ? Wb Zq (Z 4 Jet).
• Dominant SM background SM Z Jets.

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Search for t ? Zq Ingredients

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Search for t ? Zq Results

• Analysis method Fit mass ?2 in 3 regions
• Signal (B-tagged and Anti b-Tagged)
• Control
• ) Constrain shape normalization of Z jets
  background.
• Data compatible with background only.
• Feldman-Cousins limit with systematic
  uncertainties
• 3.5 times better than best
• published limit (L3)

Worlds Best Measurement!
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Looking Forward

• Top quark physics is becoming precision field.
• Almost all analyses (except mass) are still
  statistics limited.
• So far, most (but not all) things are
  frustratingly consistent with the SM.
• CDF and DØ each have many of the worlds best
  measurments
• http//www-cdf.fnal.gov/
• physics/new/top/top.html
• http//www-d0.fnal.gov/Run2Physics/
• WWW/results/top.htm
• MZ (leptophobic) gt 760 GeV (95 C.L.)
• Br (t ! Zq) lt 3.7 (95 C.L.)
• Br (t ! Invisible) lt 9 (95 C.L.)
• Lots of exciting top physics happening at the CDF
  and DØ.
• CDF, DØ, and the Tevatron are all running
  very well.
• A lot of room to grow.

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New Era of Precision Top Physics!
2006 PDG Top Entry
2008 PDG Top Entry
2010 PDG Top Entry
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Thank You!
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Backup Slides
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Top Physics Finally Makes Prime Time
The Big Bang Theory! Mondays at 700 on CBS.
Top Branching Fractions
Top FCNC
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