19-24 May 2003 K. Goulianos, CIPANP-2003 1

Konstantin GoulianosThe Rockefeller University & The CDF Collaboration

CIPANP-2003, New York City, 19-24 May 2003

• Introduction• Soft Diffraction• Hard Diffraction• Conclusion

Aspects of Diffraction at the TevatronAspects of Diffraction at the Tevatron

Selected reviews: hep-ex/0011059, hep-ex/0011060, hep-ph/0205141, hep-ph/0203217

19-24 May 2003 K. Goulianos, CIPANP-2003 2

Introduction

X

p

X

L

L

m

m

S

M

P

P

2

ξ

Diffractiondissociation

2

2

dMdtd

1

~dt

d

KG, Phys. Rep. 101 (1983) 171

cohe

rence

What is hadronic diffraction?

19-24 May 2003 K. Goulianos, CIPANP-2003 3

rapidity gaps are regions of rapidity devoid of particles

Gaps are exponentially suppressed

From Poisson statistics:

dy

dneP y )(

(r=particle density in rapidity space)

2lnlnln Msy

constant~1

~22 yd

d

MdM

d

large rapidity gaps are signatures for diffraction

rapidity gaps are formed bymultiplicity fluctuations

rapidity gaps, like diamonds,‘live for ever’

Non-diffractive interactions: Diffractive interactions:

Diffraction and Rapidity GapsDiffraction and Rapidity Gaps

19-24 May 2003 K. Goulianos, CIPANP-2003 4

Quark/gluon exchange across a rapidity gap:

POMERON

No particles radiated in the gap:

the exchange is COLOR-SINGLET with quantum numbers of vacuum

Rapidity gap formation: NON-PERTURBATIVE

Diffraction probes the large distance aspects of QCD:

POMERON CONFINEMENT

PARTONIC STRUCTURE FACTORIZATION

?

The PomeronThe Pomeron

19-24 May 2003 K. Goulianos, CIPANP-2003 5

Elastic scattering Total cross section Diffraction

PRD PRL PRL PRL50 (1994) 5535 87 (2001)141802 to be sub’d submitted

SOFT diffraction

HARD diffraction

Control sample

W 78 (1997) 2698 JJ 74 (1995) 855 JJ 85 (2000) 4217

JJ 79 (1997) 2636 JJ 80 (1998) 1156

b-quark 84 (2000) 232 JJ 81 (1998) 5278

J/ 87 (2001) 241802

JJ 84 (2000) 5043

JJ 88 (2002) 151802

with roman pots

PRL reference

PRD 50 (1994) 5518

PRD 50 (1994) 5550

Diffraction at CDF in Run IDiffraction at CDF in Run I

19-24 May 2003 K. Goulianos, CIPANP-2003 6

Hard diffraction

PLB 531(2002)52 PRL 72(1994)2332 Conference report

W-conf. report PRL 76(1996)734

PRB 440(1998)189

Diffraction at D0 in Run IDiffraction at D0 in Run I

19-24 May 2003 K. Goulianos, CIPANP-2003 7

)'(),(/

2

ytyfdtyd

dpIPpIP

Factorization & Renormalization

Soft diffraction

Renormalize to unityKG, PLB 358(1995)379

Gap probability )0(

)(

pIP

IPIPIP tg

y

y

'y

sln2ln XM

ysy ln

XM

yo e

2)(tFeC pyt

COLORFACTOR

tt '1)( PI

Pomerontrajectory

1)0(ln IPses os

ooT

parton model

19-24 May 2003 K. Goulianos, CIPANP-2003 8

X)pp(p)pp( Total cross section

KG, PLB 358 (1995) 379Differential cross section

KG&JM, PRD 59 (114017) 1999

2s

12

2

2 )(M

s

dM

dREGGE

122 )(

1

MdM

dRENORM

s-independent Differential shape agrees with Regge Normalization is suppressed by factor Renormalize Pomeron flux factor to unity

2sM2 SCALING

Soft Single Diffraction (CDF-I)Soft Single Diffraction (CDF-I)

19-24 May 2003 K. Goulianos, CIPANP-2003 9

Double Pomeron Exchange

Measure

Plot #Events versus log()

ieEs

iTp

particlesall

1

SDD: single+double diffraction Central gaps in SD events

Central and Double Gaps (CDF-I)Central and Double Gaps (CDF-I)

• Double Diffraction

• Measure #Events versus

19-24 May 2003 K. Goulianos, CIPANP-2003 10

Differential shapes agree with Regge predictions

One-gap cross sections require renormalization

DD SDD DPE

Two-gap/one-gap ratios are )17.0(

Central and Double-gap Results (CDF)Central and Double-gap Results (CDF)

19-24 May 2003 K. Goulianos, CIPANP-2003 11

1y 2y1y 2y

1y 2y

2t1t 21 yyy 5 independent variables

2122

2-1i1

2

51

5

)( yyo

ytp

ii

eetFCdV

dii

Gap probability Sub-energy cross section(for regions with particles)ye 2~Integral 2~ s

Renormalization removes the s-dependence SCALING

colorfactor

Two-gap Diffraction (hep-ph/0205141)Two-gap Diffraction (hep-ph/0205141)

19-24 May 2003 K. Goulianos, CIPANP-2003 12

Hard diffraction (Run I)

BBC 3.2<<5.9FCAL 2.4<<4.2

BBCFCAL

Tag rapidity gaps

Tag antiproton

Diffractive dijets

19-24 May 2003 K. Goulianos, CIPANP-2003 13

SINGLE DIFFRACTION DOUBLE DIFFRACTIONJetJetpp gapgap Xpp

X CDF D0

W 1.15 (0.55)

JJ 0.75 (0.10) 0.65 (0.04)

b 0.62 (0.25)

J/ 1.45 (0.25)

SD/ND gap fraction (%) at 1800 GeV DD/ND gap fraction at 1800 GeV

• All SD/ND fractions ~1%

• Gluon fraction

• Suppression by ~5 relative to HERA

15.054.0 gf

Just like ND except for the suppression due to gap formation

Hard Diffraction Using Rapidity GapsHard Diffraction Using Rapidity Gaps

19-24 May 2003 K. Goulianos, CIPANP-2003 14

),,,( 2QxtF SD

ISSUES: 1) QCD factorization > is FSD universal?

2) Regge factorization >

(not detected)

pBjx

i

eEs

xjets

iT

pBj

#

1

Bjorken-x of antiproton

),( 2QxF ND Nucleon structure function

Diffractive structure function

),,,( 2QxtF SD

),(),(),,,( 2flux

2 QftfQtF IPIPSD

/x?

momentum fraction of parton in IP

METHOD of measuring FSD : measure ratio R(,t) of SD/ND rates for given ,t set R(,t)=FSD/FND

evaluate FSD = R * FND

Diffractic Dijets with Leading (CDF)Diffractic Dijets with Leading (CDF)p

19-24 May 2003 K. Goulianos, CIPANP-2003 15

)(DJJF

mnDJJ CF ),(

Test Regge factorizationTest QCD factorization

Regge factorization holdsSuppressed at the Tevatronrelative to predictions basedon HERA parton densities exchangePomeron1m !!!

Dijets in Single Diffraction (CDF-I)Dijets in Single Diffraction (CDF-I)

19-24 May 2003 K. Goulianos, CIPANP-2003 16

(not detected)

R(SD/ND)

R(DPE/SD)

Test of factorization

equal?

SDND

DPESD RR 5

Factorization breaks down

The second gap is un-suppressed!!!

Dijets in Double Pomeron Exchange (CDF-I)Dijets in Double Pomeron Exchange (CDF-I)

19-24 May 2003 K. Goulianos, CIPANP-2003 17

Run II Diffraction at the Tevatron

CDF and D0 Forward Detectors

MiniPlug calorimeters (3.5<<5.5) Beam Shower Counters (5.5<<7.5) Antiproton Roman Pot Spectrometer

Roman Pot Spectrometers on proton & antiproton sides

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J5 At least one cal tower with ET > 5 GeV

RP inclusive Three-fold coincidence in RP trigger counters

RP+J5 Single Diffractive dijet candidates

RP+J5+BSC-GAP_p Double Pomeron Exchange dijet candidates

Triggers

Results presented are from ~26 pb-1 of data The Roman Pot tracking system was not operational for these data samples The of the (anti)proton was determined from calorimeter information:

iiT eE

s )(

towerscal

1

(-)+ is for (anti)proton

Run II Data Samples (CDF)Run II Data Samples (CDF)

19-24 May 2003 K. Goulianos, CIPANP-2003 19

R=(SD/ND

ND+SD & SD+MBoverlap events

~ 1SD

events

0.03<<0.1

Agreement with Run INo Q2 dependence

ondistributiXp

Run II Dijets in Single Diffraction (CDF)Run II Dijets in Single Diffraction (CDF)

constantlog

1

d

d

d

dFlat region

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Exclusive dijets?

Run II Dijets in DPE (CDF)Run II Dijets in DPE (CDF)

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Inclusive/Exclusive DPE Dijet Predictions Inclusive/Exclusive DPE Dijet Predictions

19-24 May 2003 K. Goulianos, CIPANP-2003 22

Run II: Exclusive DPE Dijets ?Run II: Exclusive DPE Dijets ?

No exclusive dijetbump observed

Generous upper limiton exclusive dijets

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Double Pomeron Exchange Dijet EventsDouble Pomeron Exchange Dijet Events

Rjj=0.81, Jet1(2)=33.4(31.5) GeV Rjj=0.36, Jet1(2)=36.2(33.3) GeV

19-24 May 2003 K. Goulianos, CIPANP-2003 24

SUMMARY

Soft and hard conclusionsSOFT 1) Differential shapes agree with factorization based Regge predictions

2) Single-gap production rates are suppressed as the energy increases3) Renormalizing the gap probability to unity yields correct rates4) Two-gap to one-gap ratios are ~ equal to Same general features as in soft diffraction

HARD

COLORFACTORpIPIPIPIPg /