Soft and Hard Diffraction at CDF

$: Soft and Hard Diffraction at CDF$
23-28 June 2003 K. Goulianos, Blois Workshop, Helsinki, Finland 1

Konstantin GoulianosThe Rockefeller University & The CDF Collaboration

Xth Blois Workshop on Elastic and Diffractive Scattering23-28 June 2003, Helsinki, Finland

Soft and Hard Diffraction at CDFSoft and Hard Diffraction at CDF

4-7 June 2003 K. Goulianos, Low-x Workshop, Nafplion 2

IntroductionWhat is hadronic diffraction?

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


Non-diffractive interactions: Diffractive interactions:

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’

Diffraction and Rapidity GapsDiffraction and Rapidity Gaps


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


Elastic scattering Total cross section Diffraction

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

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


Factorization & (re)normalization

Soft diffraction

)'(),(/

2

ytyfdtyd

dpIPpIP

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


X)pp(p)pp( Total cross section

KG, PLB 358 (1995) 379Differential cross section

KG&JM, PRD 59 (114017) 1999

2~ s

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 DataSoft Single Diffraction Data


Double diffraction

Plot #Events versus

Double Pomeron Exchange

Measure

Plot #Events versus log()

ieEs

iTp

particlesall

1

SDD: single+double diffraction Central gaps in SD events

Central and Double GapsCentral and Double Gaps


colorfactor

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

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


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 ResultsCentral and Double-Gap Results


Soft Double Pomeron ExchangeSoft Double Pomeron Exchange

ieEs

iTp

particlesall

1

Roman Pot triggered events

0.035 < -pbar < 0.095

|t-pbar| < 1 GeV 2

-proton measured using

Data compared to MC based

on Pomeron exchange with

Pomeron intercept =0.1

Good agreement over the entire kinematic region (4 orders of magnitude!)


Hard diffraction in Run I

BBC 3.2<<5.9FCAL 2.4<<4.2

BBCFCAL

Diffractive dijets

CDF Forward Detectors


SINGLE DIFFRACTION DOUBLE DIFFRACTIONJetJetpp gapgap Xpp

1.45 (0.25)J/

0.62 (0.25)b

0.65 (0.04)0.75 (0.10)JJ

1.15 (0.55)W

D0CDFX

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 in ND except for the suppression due to gap formation

Hard Diffraction Using Rapidity GapsHard Diffraction Using Rapidity Gaps


),,,( 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

Diffractive Dijets with Leading AntiprotonDiffractive Dijets with Leading AntiprotonThe diffractive structure function


)(DJJF

mnDJJ CF ),(

Test Regge factorizationTest QCD factorization

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

Dijets in Single DiffractionDijets in Single Diffraction


(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 ExchangeDijets in Double Pomeron Exchange


Run II Diffraction at the TevatronCDF Forward Detectors

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


Run II Forward Detector LayoutRun II Forward Detector Layout


MiniPlug Run II DataMiniPlug Run II Data

ADC counts in MiniPlug towersin a pbar-p event at 1960 GeV.• “jet” indicates an energy cluster and may be just a hadron.• Approximately 1000 counts = 1 GeVMultiplicity distribution in SD and ND events

MiniPlug tower structure


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

X eEs

)(

towerscal

1

(-)+ is for (anti)proton

Run II Data SamplesRun II Data Samples


Diffractive Dijet SampleDiffractive Dijet Sample

ND+SD & SD+MBoverlap events

~ 1SD

events

0.03<<0.1

ondistributiXp

constantlog

1

d

d

d

dFlat region


Diffractive Dijet Structure FunctionDiffractive Dijet Structure Function

Ratio of SD to ND dijet eventratesas a function of xBj

for different values of Q2=ET2

Ratio of SD to ND dijet event ratesas a function of xBj

compared with Run I data

No dependence observed within 0.03 < <0.1(confirms Run I result)

No appreciable Q2 dependence observed within 100 < Q2 < 1600 GeV


Dijets in DPEDijets in DPE

In SD data with RP+J5 triggerselect events with rapidity gapin both the BSC_p and MP_p

(3.5 < <7.5)


Data SelectionData SelectionDPE dijet candidatesDPE: RP+J5+BSC_GAP_p

Single Diffractive dijet candidatesSD: RP+J5

Tower with ET > 5 GeVND: J5

Prescale=5

Prescale=280


DPE Dijet KinematicsDPE Dijet Kinematics


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


Limit on Exclusive DPE Dijets (Run I)Limit on Exclusive DPE Dijets (Run I)

σ

CL)(95%nb3.7e)σ(exclusiv

nb21.6(syst)stat)(4.444.6e)σ(inclusiv

Observed ~100 DPE dijet events

0.035 < < 0.095 Jet ET > 7 GeV Rapidity gap in 2.4 < < 5.9

Dijet mass fraction X

jjjj M

MR

MJJ based on energy within cone of 0.7=> look for exclusive dijets in window 0.7 < RJJ < 0.9


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

No exclusive dijetbump observed


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


SUMMARYSoft and hard conclusions

Soft Diffraction

Hard Diffraction Pay a color factor for each gap

Use the reduced energy cross section

Get gap size from renormalized Pgap

Diffraction is an interaction between low-x partons subject to color constraints

Soft and Hard Diffraction at CDF

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