Results from CDF on Diffraction

1
Results from CDF on Diffraction
K. Goulianos The Rockefeller University
? presented on behalf of the CDF collaboration ?
Workshop on Low x PhysicsLisbon, Portugal, 28
June 1 July, 2006
2
Contents

• Introduction Run I results
• Run II results
• Exclusive Production
• Diffractive structure function

3
p-p Interactions
Diffractive Colorless exchange with vacuum qu
antum numbers
Non-diffractive Color-exchange
rapidity gap
Incident hadrons retain their quantum numbers
remaining colorless
pseudo- DECONFINEMENT
Goal understand the QCD nature of the
diffractive exchange
4
Rapidity Gaps
ln s
f
Particle production
Rapidity gap
-ln x
ln MX2
h
5
Diffraction _at_ CDF
sTIm fel (t0)
Elastic scattering
Total cross section
f
f
OPTICAL THEOREM
GAP
h
h
DD
DPE
SDDSDDD
SD
6
Gaps in the sky!
7
Run 1-0 (1988-89)
Elastic, single diffractive, and total cross
sections
_at_ 546 and 1800 GeV
Roman Pot Spectrometers
CDF-I

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

Roman Pots with Trackers up to h 7

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

8
Renormalization
Factorization ?
Pomeron flux

• Regge theory
• sSD exceeds sT at
• Renormalization
• Pomeron flux integral
• (re)normalized to unity

KG, PLB 358 (1995) 379
9
A Scaling Law in Diffraction
KGJM, PRD 59 (1999) 114017
? Independent of S over 6 orders of magnitude in
M2 !
Factorization breaks down so as to ensure
M2-scaling!
10
The QCD Connection
f
Total cross section power law increase versus s
y
1/as
The exponential rise of sT(Dy) is due
to the increase of wee partons with Dy
(E. Levin, An Introduction to Pomerons,Preprint
DESY 98-120)
Elastic cross section forward scattering amplitu
de
11
Single Diffraction in QCD
(KG, hep-ph/0205141)
t
2 independent variables
color factor
Gap probability
Renormalization removes the s-dependence
SCALING
12
Multi-gap Renormalization
(KG, hep-ph/0205141)
13
CDF-IA, IB
beam
Forward Detectors BBC 3.24.2
14
Central and Double Gaps

• Double Diffraction Dissociation
• One central gap

• Double Pomeron Exchange
  
  
• Two forward gaps

• SDD SingleDouble Diffraction
• One forward one central gap

15
Central Double-Gap CDF Results
16
CDF-IC
beam
Forward Detectors BBC 3.24.2
17
HARD DIFFRACTION

• Diffractive fractions
• Diffractive structure function
• ? factorization breakdown
• Restoring factorization
• Hard diffraction in QCD

JJ, W, b, J/y
18
Diffractive Fractions
Fraction()
Fraction SD/ND ratio at 1800 GeV
All ratios 1 ? uniform suppression
FACTORIZATION !
1.15 (0.55)
W
0.75 (0.10)
JJ
0.62 (0.25)
b
1.45 (0.25)
J/y
19
Diffractive Structure FunctionBreakdown of QCD
Factorization
b momentum fraction of parton in Pomeron
The diffractive structure function at the
Tevatron is suppressed by a factor of 10
relative to expectation from pdfs measured by H1
at HERA Similar suppression factor as in
soft diffraction relative to Regge expectations!

H1
CDF
Using preliminary pdfs from
20
Restoring QCD Factorization
The diffractive structure function measured on
the proton side in events with a leading
antiproton is NOT suppressed relative to
predictions based on DDIS
21
CDF-II
22
The MiniPlugs _at_ CDF
23
MiniPlug Calorimeter
About 1500 wavelength shifting fibers of 1 mm
dia. are strung through holes
drilled in 36x¼ lead plates sandwiched between
reflective Al sheets and guided
into bunches to be viewed individually by
multi-channel photomultipliers.
24
Run II Results

• Diffractive structure function
• Q2 - dependence
• t - dependence
• Exclusive production
• dijet
• diphoton

25
Diffractive Dijet Signal

• - Bulk of data taken with RPS trigger but no
  working RPS tracking
  
• Extract x from calorimetric information
• Calibrate calorimetric x using limited sample of
  RPS tracking data
  
• Subtract overlap background using a rescaled
  dijet event sample
  
• Verify diffractive x range by comparing xRPS
  with xCAL
  

Overlap events mainly ND dijets plus SD low x
RPS trigger
26
xCAL Calibration
overlap events
signal region
xcal distribution for slice of xRPS
? / mean 30
27
Dijet Properties
SD boosted opposite to pbar
28
Alignment of RPS using Data
maximize the t-slope ? determine X and Y offset
s
29
Diffractive Structure FunctionQ2 dependence
ETjet 100 GeV !

• Small Q2 dependence in region 100 GeV2
  
• Pomeron evolves similarly to proton!

30
Diffractive Structure Functiont- dependence
Fit ds/dt to a double exponential

• No diffraction dips
• No Q2 dependence in slope
• from inclusive to Q2104 GeV2

• Same slope over entire region of
• 0
• across soft and hard diffraction!

31
EXCLUSIVE PRODUCTION
Measure exclusive jj gg ? ?
? Calibrate predictions for

H production
rates _at_ LHC
Bialas, Landshoff, Phys.Lett. B 256,540 (1991) K
hoze, Martin, Ryskin, Eur. Phys. J. C23, 311 (200
2) C25,391 (2002)C26,229 (2002)
C. Royon, hep-ph/0308283 B. Cox, A. Pilkington,
PRD 72, 094024 (2005) OTHER
KMR sH(LHC) 3 fb S/B 1 if DM 1 GeV
Clean discovery channel
Search for exclusive gg Search for events with
two high ET gammas and no other activity in the
calorimeters or BSCs

Search for exclusive dijets Measure dijet mass f
raction
Look for signal as Mjj? 1
32
Exclusive Dijet and gg Search
b-taqged dijet fraction
Dijet fraction all jets
DIJETS
Exlusive b-jets are suppressed
by JZ 0 selection rule
Excess over MC predictions at large dijet mass f
raction
Systematic uncertainties under study tune in
soon for results!
Exclusive gg Based on 3 events observed Goo
d agreement with KMR
33
Dijets Data vs MC
Exclusive DPE (DPEMC) ? non-pQCD based on Regge t
heory
ExHuME (KMR) gg?gg process ? uses LO pQCD

• Excess of events at high Rjj is well described by
  both exclusive dijet production models
  
• Currently investigating the dependence of the
  cross section on second jet ET to differentiate
  between the two models

34
Exclusive Dijet Signal
COMPARISON inclusive data vs MC _at_ b/c-jet data vs
inclusive
35
Exclusive gg/ee Search
QED process cross-check to exclusive gg

• (anti)proton not detected
• require 2 EM showers (ET5 GeV, h
• veto on all BSCs and all calorimetery except for
  the 2 EM showers
  
• L530 pb-1 delivered ? Leffective46 pb-1
• ? 19 events with 2 EM showers nothing above
  threshold

36
Exclusive ee Search
control sample for gg search
ET16.1 GeV ET26.0 GeV
?16 candidate events found background
good agreement with LPAIR
37
Exclusive gg Search
? 3 candidate events found background
ET16.8 GeV/c ET25.9 GeV/c
good agreement with KMR
? sH 10 fb (if H exists) within a factor 2-3
, higher in MSSM
38
Dark Energy
39
Summary

• TEVATRON what we have learnt
• M2 scaling
• Non-suppressed double-gap to single-gap ratios
• Pomeron composite object made up from
  underlying
  
• pdfs subject to color constraints
• LHC - what to do
• High mass (? 4 TeV !) and multi-gap diffraction
  
  
• Exclusive production
• ? Reduced bgnd for std Higgs to study
  properties
  
• ? Discovery channel for certain Higgs
  scenarios

40
BACKUP
41
Diffractive DIStwo models
Particle-like Pomeron
Color reorganization
probing the proton structure!
what is the Pomeron structure?
42
Inclusive vs Diffractive DIS
KG, Diffraction a New Approach,
J.Phys.G26716-720,2000 e-Print Archive
hep-ph/0001092
Inclusive DIS
Inclusive diffr. DIS
aP(0)-1
(eql)/2
43
DSF H1 vs ZEUS
H1
CDF
Using preliminary pdfs from
44
Diffractive Dijets _at_ Tevatron
eg 0.2 ? Agreement with data!
45
x-dependence Inclusive vs Dijet
46
Gap Between Jets
47
Diffraction from the Deep Sea
deep sea
valence quarks
Derive diffractive from inclusive PDFs and color
factors
xx
proton