K. GoulianosThe Rockefeller University

EDS 200515-20 May 2005

Chateau de Blois, France

Twenty Years of Diffractionat the Tevatron

http://physics.rockefeller.edu/dino/my.html

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 2

-p Interactions

Diffractive:

vacuum exchange

Protons retain theirquantum numbers

Non-diffractive:

color exchange

Protons acquire colorand break apart

p

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 3

Why StudyParticle Diffraction?

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 4

Asymmetric Fireworks?Po’< Po

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 5

Non-perturbative QCD

THEORY

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!

experiment

phenomenology

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 6

1960’s BNL: first observation of pp -> pX

1970’s Fermilab fixed target, ISR, SPS Regge theory & factorization

Review: KG, Phys. Rep. 101 (1983) 169

1980’s UA8: diffractive dijets hard diffraction

1990’s Tev Run-I: Regge factorization breakdownTev vs HERA: QCD factorization breakdown

21st C Multigap diffraction: restoration of factorizationIdeal for diffractive studies @ LHC

Forty Years of DiffractionTwenty Years at the Tevatron

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 7

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

Roman Pot Spectrometers

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

Results Total cross section tot ~ s Elastic cross section d/dt ~ exp[2’ lns] shrinking forward peak Single diffraction Breakdown of Regge factorization

Additional DetectorsTrackers up to || = 7

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 8

Run 1-0 results in perspective

KG, PLB 358 (1995) 379

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 9

CDF Run 1 (1992-1995)

Run-IC Run-IA,B

Forward DetectorsBBC 3.2<<5.9FCAL 2.4<<4.2

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 10

Diffraction @ CDF in Run I

93(2004)141601

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 11

All ratios ~ 1% ~ uniform suppression

~ FACTORIZATION

Diffractive Fractions @ CDF

gap)( XHdpp

1.45 (0.25)J/

0.62 (0.25)b

0.75 (0.10)JJ

1.15 (0.55)W

Fraction(%)Hd

Fraction:SD/ND ratioat 1800 GeV

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 12

Tevatron vs HERA:Breakdown of QCD Factorization

CDF

H1

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 13

Multigap Diffraction

1y 2y1y 2y

1y 2y

(KG, hep-ph/0205141)

y

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Elastic and Total Cross Sections

QCD expectations

ytel etsf ),(Im

y sy ln

Elastic cross section:forward scattering amplitude

The exponential rise of T(y’) is dueto the increase of wee partons with y’

(see E. Levin, An Introduction to Pomerons,Preprint DESY 98-120)

yooT ess )(

y sy ln

Total cross section:power law rise with energy

s

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 15

Gap probability MUST be normalized to unity!

Single Diffraction

yy

yt ,2 independent variables:

t

colorfactor

17.0)0(

)(

ppIP

IPIPIP tg

yo

ytp eetFC

yddt

d

222

)(

gap probability sub-energy x-section

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 16

Single diffraction (re)normalized

yo

ytpgap eetFCN

yddt

d

222

)(

s

sCdtydtyPsN s

gaptygap ln),()(

2

,1

tybys eseCyddt

d )2()(ln2

0ln

No unitarity problem after eikonalization of the elastic amplitude

Grows slower than lns

),( tyPgap

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 17

Total Single Diffractive x-Section

Unitarity problem: Using factorization and std pomeron flux SD exceeds T at Renormalization: Normalize the Pomeron flux to unity

)(sσξ)(t,fdtdξ

σdpIPIP/p

SD2

KG, PLB 358 (1995) 379

TeV.2s

1dtdξξ)(t,f0.1

ξ

IP/p

0

tmin

2~ sSD

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 18

The Factors and Experimentally: KG&JM, PRD 59 (114017) 1999

g=0.20

q=0.04

R=-0.5

fg=gluon fractionfq=quark fraction

λx

1f(x)x

18.03

125.0

8

175.0

121f

1

1f

2

Q

NN cq

cgColor factor:

12.0ww qqgg Pomeron intercept:

104.0,02.017.0

pIP

IPIPIPg

λ

/sxs~dxxf

1

1)(

CTEQ5L

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Multigap Cross Sections

ssty ln/2~,

Same suppressionas for single gap!

2122

2-1i1

2

51

5

)( yyo

ytp

ii

eetFCdV

dii

Gap probability Sub-energy cross section(for regions with particles)

1y 2y1y 2y

1y 2y

1t 21 yyy 5 independent variables2t color

factors

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Central and Two-Gap CDF Results

One-gap cross sections are suppressed Two-gap/one-gap ratios are 17.0

Agreement with renormalized Regge predictions

DD SDD DPE

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Gap Survival Probability

0.23GeV)(1800S gapgap/01gapgap/12

0.29GeV)(630S gapgap/01gapgap/12

S =

Results similar to predictions by:Gotsman-Levin-MaorKaidalov-Khoze-Martin-RyskinSoft color interactions

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 22

),(),(),,( 22

22)3(2

2 QQQ xFmfxF hadronqD

Diffractive DIS @ HERA

eQ2*

p

jet

reorganize

Factorization holds: J. Collins

e*

tp

IP

Pomeron exchange Color reorganization

Brodsky et al. rescattering?

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 23

Inclusive vs Diffractive DIS

Rq Q

Q

QRqRq Q

Q

Rq

DCC

F Q, ,1

,,1

05.02)3(2

2

2

22

2 1

)(

1),,(

P(0)-1(q)/2

F2 ~ x

q

g=0.20

q=0. 04

R=-0.5

KG, “Diffraction: a New Approach,” J.Phys.G26:716-720,2000 e-Print Archive: hep-ph/0001092

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 24

Diffractive Dijets @ Tevatron

),/(1

),,( 22

21 QQ xFxFsoft

D

pjet

reorganizep

jet

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FDJJ(,Q2) @ Tevatron

2sβ

ξ

dξN

ε

ε

2sβ

1

β

xξ1

ξ 211

renorm

minmin

min

)2(

)(1

12

2R

2RENORM

xQs

xSDND

4.02.0 xg

)()(renorm

22

2

2

2 )(12

)/(

)(1N),,( 21221 Q

Q

Q

QQ

C

sx

CF D

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 26

SD/ND Dijet Ratio vs xBj@ CDF

(x)F

(x)FR(x) ND

jj

SDjj

0.035 < < 0.095

Flat dependence

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Restoring Factorization @ Tevatron

R(SD/ND)

R(DPE/SD)

DSF from two/one gap:factorization restored!

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 28

Gap Between Jets

5%0.2

1%

S

R)s(R

JGJTEVJGJ

LHC

JetGapJetpp

1%/)s(R JGJTEV

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 29

Gap Between Jets

jet???gap ΔyΔy Question

gapΔyjetΔy

JetGapJetpp

Is the diffractive exchange BFKL-likeor simply a color rearrangement?

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 30

valence quarks

antiproton

x=

Low-x and Diffraction

proton

)or(1

)( xxfx

g=0.20

q=0. 04

R=-0.5

g=0.5

q=0.3

SOFT HARD

deep sea

Derive diffractivefrom inclusive PDFsand color factors

antiproton

valence quarks

p

p

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 31

Run 2 CDF Diffractive Program

Single Diffraction and Q2 dependence of Fjj

D

Process dependence of FD (W, J/ Double Diffraction Jet-Gap-Jet: gap for fixed large jet

Double Pomeron Exchange Fjj

D on p-side vs -pbar

Also:Exclusive central production Dijets, c

Other Tev4LHC issues

EDS 2005, 15-20 May 2005 Twenty Years of Diffraction at the Tevatron K. Goulianos 32

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 pdf’s of the (anti)proton. This picture could be further clarified and advanced to a theory by studies at the LHC.