Diffraction at the Tevatron

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Diffraction at the Tevatron
XXXIII International Conference on High Energy
Physics Moscow 28 July 2006
Andrew Hamilton Université de Genève for the CDF
and D? Collaborations
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Introduction
Diffraction An exchange with the quantum numbers
of the vacuum.
introduction
Non-Diffractive
Diffraction
Color Exchange
Vacuum QN Exchange

• Goals of Diffractive Program at the Tevatron
• Understand the nature of diffractive exchange
• Test the feasibility of diffraction as a tool to
  search for new physics at the LHC

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Outline
outline

• Diffraction at D?
• physics plans
• Inclusive Diffraction at CDF
• ratio of SD/ND dijets
• Q2 dependence of t in SD dijets
• Exclusive Production at CDF
• two mechanisms (QED and QCD)
• searches for QED mediated ee-
• searches for QCD mediated ?? and dijets
• Summary

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Diffraction at D?

• Diffractive Analyses in Progress at D?
• Double Pomeron Exchange (DPE) Jets
• Diffractive Structure Function
• Diffractive Heavy Flavor
• Exclusive Production
• Diffractive Z
• Diffractive W
• Inclusive DPE

D? plans
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Inclusive Diffraction at CDF
CDF inclusive intro
Use high pT jets as a probe to measure
Diffractive Structure Function, FjjD
Pomeron
? Ppomeron / Pproton
t ( Pi - Pf )2
? Pparton / PPomeron
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Inclusive Diffraction Results

• No Q2 dependence
• (100 lt Q2 lt 10000 GeV2)
• The Pomeron evolves like the proton

CDF inclusive results

• Slope of d?/dt is independent of Q2 in SD dijets

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Exclusive Production at CDF

• Exclusive Production QED or QCD mediated

CDF exclusive intro
QED
QCD

• measure exclusive QCD dijet and ?? production at
  Tevatron to constrain predictions on exclusive
  Higgs at LHC

• measure exclusive QED ee- and ??- production at
  Tevatron to test feasibility of Luminosity
  measurement at LHC

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QED Mediated ee- Production

• Exclusive ee- events are selected by
• reconstructing the ee-
• requiring that there is no other activity in
  ?lt7.4
• protons are not tagged

CDF exclusive ee-
Tower Threshold 30 MeV
16 events similar are found.
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QED Mediated ee- Production
CDF exclusive ee-

• Background estimate 2.10.7
• ?exp 1.6 0.5 (stat) 0.3 (sys) pb
• ?LPAIR 1.711 0.008 pb

-0.3
-
-0.3
-
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QCD Mediated ?? Production

• Exclusive ?? events
• selected in the same way as ee- (except
  tracking)
• agreement of exclusive ee- cross section gives
  confidence in analysis methodology

CDF exclusive ??
Tower Threshold 30 MeV
3 events are found.
Background estimate is not yet complete
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QCD Mediated Dijet Production

• Strategy

• select DPE dijets p p ? p X (?2jets) gap
• examine the dijet mass fraction Rjj

CDF exclusive
Similar for DPEMC
dijet
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QCD Mediated Dijet Production

• Another Observable
• exclusive gg ? qq is suppressed by JZ0 rule
• exploit this by looking at fraction of heavy
  flavor (b/c) jets in dijet data as a function of
  Rjj

CDF exclusive
b/c jets suppressed at high Rjj
the two observables agree
dijet
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QCD Mediated Dijet Production
CDF exclusive
How does the cross section compare?

• The data favors ExHuME MC

dijet
Ratio of exclusive to inclusive DPE cross
sections is flat.
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Summary

• Diffraction at D?
• many analyses in progress
• Inclusive Diffraction at CDF
• Q2 dependence of Diffractive Structure Function
• slope of SD dijet d?/dt is independent of Q2
• Exclusive Production at CDF
• observed ee- production via QED exchange
• possible evidence for ?? production via QCD
  exchange
• observed dijet production via QCD exchange
• KMR / ExHuME predictions are consistent with data
• see previous talk for impact KMR of predictions
  on the LHC

summary
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Backup Slides

• Backup Slides

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Tevatron Luminosity
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Forward Detectors
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ee Numbers
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ee Numbers
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ee Plots
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Dijet Plots
DATASETS Exclusive / Inclusive fraction 310
pb-1 Heavy Flavor fraction 200 pb-1
ExHuME
DPEMC
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Dijet Plots
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Dijet Plots
B
B
A
A
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Dijet Cross Section