Search for Compositeness at the Tevatron

1
Search for Compositeness at the Tevatron

• Iain A. Bertram
• Northwestern University/DØ

2
Talk Outline

• Introduction
• Direct Search for Composite Quarks
• Contact Interaction Searches
• Quark-Quark Compositeness Dijet Events
• Quark-Lepton Compositeness Drell-Yan Events
• Run II Prospects
• Conclusion

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Introduction

• Three quark and lepton generations suggests that
  quark and leptons are composites.
• Composed of PREONS.
• Preons interact via a new strong interaction
  (Metacolour).
• Below a characteristic energy scale ?, the preons
  form metacolour singlets quarks and leptons.
• Strength of interactions related to

Atom
Nucleus
Nucleon
Quark
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Effective Lagrangian
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Dijet and Dielectron Variables

• Dijet and di-electron Event Measure the following

Jet, electron 1 ET1, h1, ?1
Jet, electron 2 ET2, h2, ?2
h 0
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Typical DØ Dijet Event
ET,1 475 GeV, h1 -0.69, x10.66 ET,2 472
GeV, h2 0.69, x20.66
MJJ 1.18 TeV Q2 2.2x105
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Typical CDF Drell-Yan Event
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Dijet Drell-Yan Production

• To search for compositeness we need a good
  prediction for Standard Model production
• Dijets NLO event generator JETRAD, Giele,
  Glover, Kosower Nucl. Phys. B403, 633.
• Drell Yan NNLO CalculationHamberg, Van Neerven,
  Matsuura, Nucl. Phys. B359 343.
• Need to choose pdf
• Choose Renormalization and Factorization scales
  (set equal)
• Jets Rsep maximum separation allowed between
  two partons to form a jet (mimic exp.
  algorithm)Rsep1.3R (Snowmass Rsep2.0R)

1.3R
2R
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Compositeness Contact Predictions

• ? 1 ?? destructive interference
• ? -1 ??- constructive interference
• Only leading order calculationUse to scale
  highest order QCD calculations.
• Dijets Use NLO Jetrad prediction as basis
• Drell-YanUse Hamburg et al., NNLO calculation as
  a basis.

• Compositeness CalulationsEichten et al., Rev.
  Mod. Phys. 56, 579 (84) Eichten et al., Phys.
  Rev. Lett 50, 811 (83)Chivukula et al., Phys.
  Lett. B 380, 92 (96)Lee, Phys. Rev. D 55, 2591
  (97)Lane, hep-ph/9605257 (96)

M
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Colorons

• Colorons (R.S. Chivukula, A.G. Cohen and E.H.
  Simmons, hep-ph/9603311,Phys. Lett. B380 92
  (1996)
• Produces similar effects to compositeness.
• Motivated by technicolor
• Add additional SU(3) QCD type group.
• Symmetry breaking between this and standard QCD
  SU(3) leads to an additional set of massive
  gluons called colorons
• Can be modeled in a similar way to compositeness

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Search for Excited Quarks

• Search for excited quarks in dijet mass spectrum
  motivated by UA2s observation of W,Z ? JJ (Zeit.
  Phys. C49)In proton anti-proton collisions.

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Search for Excited Quarks

• PYTHIA, fffs1.0, LMq, Contact terms
  only.Smeared with Jet Resolutions, CTEQ3L
  PDF.Baur et al Phys. Rev. D42, 815 (90)

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Search for Excited Quarks

• Select data at central rapidity
• DØ hjet lt 1.0, Dhjet lt 1.6
• 104 pb-1
• Use Bayes Theorem to fit Jetrad NLO QCD
  prediction q line shape to data
• CDF hjet lt 2.0, cos?? lt 2/3
• 106 pb-1
• Phys. Rev. D55, 5263 (1997)
• Phys. Rev. Lett. 74, 3539 (1995)
• Fit data with Ansatz Function q line shape.

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Search for Excited Quarks
CDF Exclude Mq up to 570 GeV between 580 760
GeV
DØ Mq gt 725 GeV
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Search for Excited Quarks
Combined Limits Mq gt 760 GeV
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Search for Quark-Quark Compositeness

• Dijet Angular Distribution

Compositeness produces excess of events at small
? and large mass
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Search for Quark-Quark Compositeness

• Optimize for compositenessDØ X4 CDF X2.5

• Define

CDF Phys. Rev. Lett.77, 5336, 1996,
Erratum-ibid.78, 4307, 1997
DØ Phys. Rev. Lett. 80, 666,1998.
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Dijet Angular Limits
Compositeness Limits
DØ Coloron Mass Limits Mc/cot? gt 759 GeV LV8 gt
2.1 TeV
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Dijet Mass Spectrum at DØ

• Calculate Ratio of Cross Sections.
• Analgous to R?

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DØ Dijet Mass Spectrum
Accepted by PRL hep-ex/9807014
?LL1 ?LL-1 ?????? TeV ?-???4 TeV
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Quark-Quark Compositeness Limits
Coloron Limit Mc/cot? gt 837 GeV (hep-ph/9809472)
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Drell-Yan Production

• DØ measures the Drell-Yan Cross section at high
  dielectron mass.
• 120 pb-1 data
• h lt 1.1, 1.5 lt h lt 2.5
• Submitted to PRL hep-ex/9812010

• CDF measures the Drell-Yan Cross section at high
  dielectron and dimuon mass.
• 110 pb-1 data h lt 1.0
• Phys. Rev. Lett. 79, 2198, 1997.

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High Mass Drell-Yan Compositeness
DØ Data
CDF Data
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Quark-Electron Compositeness Limits
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Run II Expectations

• Assume that we will collect 2 fb-1 of data at 2
  TeV
• M gt510 GeV 2 fb-1
• M gt390 GeV 1 fb-1
• M gt300 GeV 0.25 fb-1
• M gt200 GeV 0.05 fb-1

• Assume Run 1 Systematics (5)
• Place limits using coloron model
• No optimization of bins(M gt 500 GeVgt550 events
  h lt 0.5, gt800 events 0.5 lt h lt 1.0)

Limits LV8 gt 3 TeV (cf 2.3) No Optimization
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Conclusions

• No evidence for Compositeness found at the
  Tevatron
• QCD in excellent agreement with the data
• Quark-Quark Compositeness
• ? gt 2 to 3 TeV depending on models
• Colorons Mc/cot? gt 837 GeV
• Quark-Electron Compositeness
• ? gt 3 to 6 TeV depending on model
• Very Large Data Set in Run II A Good
  Opportunity to find New Physics....