Twenty Years of Diffraction at the Tevatron

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Twenty Years of Diffractionat the Tevatron
K. Goulianos The Rockefeller University EDS
2005 15-20 May 2005 Chateau de Blois, France
http//physics.rockefeller.edu/dino/my.html
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-p Interactions
Diffractive vacuum exchange
Non-diffractive color exchange
Protons retain their quantum numbers
Protons acquire color and break apart
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Why StudyParticle Diffraction?
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Asymmetric Fireworks?
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Non-perturbative QCD

• Important for understanding hadron structure
  and quark confinement
• Need to develop new mathematical methods
• Diffraction offers an arena on which to
  confront non-pQCD

pure thinking!
THEORY
phenomenology
experiment
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Forty Years of DiffractionTwenty Years at the
Tevatron

• 1960s BNL first observation of pp -gt pX
• 1970s Fermilab fixed target, ISR, SPS
• ? Regge theory factorization
• Review KG, Phys. Rep.
  101 (1983) 169
• 1980s UA8 diffractive dijets a hard
  diffraction
• 1990s Tev Run-I Regge factorization
  breakdown
• Tev vs HERA QCD factorization breakdown
• 21st C Multigap diffraction
  restoration of factorization
• Ideal for diffractive studies _at_ LHC

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CDF Run 1-0 (1988-89)
Elastic, single diffractive, and total cross
sections
_at_ 546 and 1800 GeV
Roman Pot Spectrometers

• Roman Pot Detectors
• Scintillation trigger counters
• Wire chamber
• Double-sided silicon strip detector

Additional Detectors Trackers up to h 7

• Results
• Total cross section stot se
• Elastic cross section ds/dt exp2a
  lns ? shrinking forward peak
• Single diffraction Breakdown of Regge
  factorization

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Run 1-0 results in perspective
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CDF Run 1 (1992-1995)
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Diffraction _at_ CDF in Run I
93(2004)141601
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Diffractive Fractions _at_ CDF
All ratios 1 ? uniform suppression
FACTORIZATION
Fraction SD/ND ratio at 1800 GeV
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Tevatron vs HERABreakdown of QCD Factorization
H1
CDF
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Multigap Diffraction
(KG, hep-ph/0205141)
f
y
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Elastic and Total Cross Sections
QCD expectations
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Single Diffraction
sub-energy x-section
gap probability
Gap probability MUST be normalized to unity!
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Single diffraction (re)normalized
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Total Single Diffractive x-Section

• Unitarity problem
• Using factorization
• and std pomeron flux
• sSD exceeds sT at
• Renormalization
• Normalize the Pomeron
• flux to unity

KG, PLB 358 (1995) 379
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The Factors k and e
Experimentally
KGJM, PRD 59 (114017) 1999
CTEQ5L
fggluon fraction fqquark fraction
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Multigap Cross Sections
Same suppression as for single gap!
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Central and Two-Gap CDF Results
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Gap Survival Probability
Results similar to predictions by Gotsman-Levin-M
aor Kaidalov-Khoze-Martin-Ryskin Soft color
interactions
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Diffractive DIS _at_ HERA
Factorization holds J. Collins
Pomeron exchange
Color reorganization
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Inclusive vs Diffractive DIS
KG, Diffraction a New Approach,
J.Phys.G26716-720,2000 e-Print Archive
hep-ph/0001092
F2 x-l
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Diffractive Dijets _at_ Tevatron
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FDJJ(x,b,Q2) _at_ Tevatron
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SD/ND Dijet Ratio vs xBj_at_ CDF
0.035 lt x lt 0.095
Flat x dependence
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Restoring Factorization _at_ Tevatron
DSF from two/one gap factorization restored!
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Gap Between Jets
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Gap Between Jets
Is the diffractive exchange BFKL-like or simply a
color rearrangement?
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Low-x and Diffraction
deep sea
valence quarks
Derive diffractive from inclusive PDFs and color
factors
xx
proton
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Run 2 CDF Diffractive Program

• Single Diffraction
• x and Q2 dependence of FjjD
• Process dependence of FD (W, J/y)
• Double Diffraction
• Jet-Gap-Jet Dhgap for fixed large Dhjet
• Double Pomeron Exchange
• FjjD on p-side vs x-pbar
• Also
• Exclusive central production
• Dijets, cc
• Other
• Tev4LHC issues

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Summary

• Diffraction is a low-x QCD phenomenon subject
  
• to color constraints.
• Multigap processes offer the opportunity
• to study diffraction without complications
• arising from rapidity gap survival issues.
  
• Regularities observed in Run 1
• at the Tevatron and in results
• obtained at HERA paint a picture of the
  Pomeron
• as a composite object constructed from the
  
• underlying inclusive pdfs of the
  (anti)proton.
• This picture could be further clarified
  and
• advanced to a theory by studies at the
  LHC.