Twenty years of diffraction at the tevatron
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Twenty Years of Diffraction at the Tevatron. K. Goulianos The Rockefeller University EDS 2005 15-20 May 2005 Chateau de Blois, France. http://physics.rockefeller.edu/dino/my.html. - p Interactions. Diffractive: vacuum exchange. Non-diffractive: color exchange. Protons retain their

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Twenty years of diffraction at the tevatron

Twenty Years of Diffractionat the Tevatron

K. Goulianos

The Rockefeller University

EDS 2005

15-20 May 2005

Chateau de Blois, France

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


P interactions

-p Interactions

Diffractive:

vacuum exchange

Non-diffractive:

color exchange

Protons retain their

quantum numbers

Protons acquire color

and break apart

Twenty Years of Diffraction at the Tevatron K. Goulianos


Why study particle diffraction

Why StudyParticle Diffraction?

Twenty Years of Diffraction at the Tevatron K. Goulianos


Asymmetric fireworks

Po’< Po

Asymmetric Fireworks?

Twenty Years of Diffraction at the Tevatron K. Goulianos


Non perturbative qcd

Non-perturbative QCD

  • 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!

THEORY

phenomenology

experiment

Twenty Years of Diffraction at the Tevatron K. Goulianos


Forty years of diffraction twenty years at the tevatron

Forty Years of DiffractionTwenty Years at the Tevatron

  • 1960’sBNL: first observation of pp -> pX

  • 1970’sFermilab fixed target, ISR, SPS

  •  Regge theory & factorization

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

  • 1980’sUA8: diffractive dijets a hard diffraction

  • 1990’sTev Run-I: Regge factorization breakdown

  • Tev vs HERA: QCD factorization breakdown

  • 21st C Multigap diffraction: restoration of factorization

    • Ideal for diffractive studies @ LHC

Twenty Years of Diffraction at the Tevatron K. Goulianos


Cdf run 1 0 1988 89

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

Additional Detectors

Trackers up to |h| = 7

  • Results

  • Total cross section stot ~ se

  • Elastic cross section ds/dt ~ exp[2a’ lns]  shrinking forward peak

  • Single diffraction Breakdown of Regge factorization

Twenty Years of Diffraction at the Tevatron K. Goulianos


Run 1 0 results in perspective

KG, PLB 358 (1995) 379

Run 1-0 results in perspective

Twenty Years of Diffraction at the Tevatron K. Goulianos


Cdf run 1 1992 1995

Run-IC

Run-IA,B

Forward Detectors

BBC 3.2<h<5.9

FCAL 2.4<h<4.2

CDF Run 1 (1992-1995)

Twenty Years of Diffraction at the Tevatron K. Goulianos


Diffraction @ cdf in run i

Diffraction @ CDF in Run I

93(2004)141601

Twenty Years of Diffraction at the Tevatron K. Goulianos


Diffractive fractions @ cdf

Hd

Fraction(%)

W

1.15 (0.55)

JJ

0.75 (0.10)

b

0.62 (0.25)

J/y

1.45 (0.25)

Diffractive Fractions @ CDF

Fraction:

SD/ND ratio

at 1800 GeV

All ratios ~ 1%

~ uniform suppression

~ FACTORIZATION

Twenty Years of Diffraction at the Tevatron K. Goulianos


Tevatron vs hera breakdown of qcd factorization

Tevatron vs HERA:Breakdown of QCD Factorization

H1

CDF

Twenty Years of Diffraction at the Tevatron K. Goulianos


Multigap diffraction

Multigap Diffraction

(KG, hep-ph/0205141)

f

y

Twenty Years of Diffraction at the Tevatron K. Goulianos


Elastic and total cross sections

f

y

Total cross section:

power law rise with energy

~1/as

The exponential rise of sT(Dy’) is due

to the increase of wee partons with Dy’

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

f

Elastic cross section:

forward scattering amplitude

y

Elastic and Total Cross Sections

QCD expectations

Twenty Years of Diffraction at the Tevatron K. Goulianos


Single diffraction

t

2 independent variables:

color

factor

Single Diffraction

sub-energy x-section

gap probability

Gap probability MUST be normalized to unity!

Twenty Years of Diffraction at the Tevatron K. Goulianos


Single diffraction re normalized

Grows slower than lns

 No unitarity problem after eikonalization of the elastic amplitude

Single diffraction (re)normalized

Twenty Years of Diffraction at the Tevatron K. Goulianos


Total single diffractive x section

Total Single Diffractive x-Section

  • Unitarity problem:

    Using factorization

    and std pomeron flux

    sSD exceeds sT at

  • Renormalization:

    Normalize the Pomeron

    flux to unity

KG, PLB 358 (1995) 379

Twenty Years of Diffraction at the Tevatron K. Goulianos


The factors k and e

Color factor:

Pomeron intercept:

lg=0.20

lq=0.04

lR=-0.5

The Factors k and e

Experimentally:

KG&JM, PRD 59 (114017) 1999

CTEQ5L

fg=gluon fraction

fq=quark fraction

Twenty Years of Diffraction at the Tevatron K. Goulianos


Multigap cross sections

5 independent variables

color

factors

Gap probability

Sub-energy cross section

(for regions with particles)

Multigap Cross Sections

Same suppression

as for single gap!

Twenty Years of Diffraction at the Tevatron K. Goulianos


Central and two gap cdf results

Agreement with renormalized Regge predictions

DD

SDD

DPE

  • One-gap cross sections are suppressed

  • Two-gap/one-gap ratios are

Central and Two-Gap CDF Results

Twenty Years of Diffraction at the Tevatron K. Goulianos


Gap survival probability

S =

Gap Survival Probability

Results similar to predictions by:

Gotsman-Levin-Maor

Kaidalov-Khoze-Martin-Ryskin

Soft color interactions

Twenty Years of Diffraction at the Tevatron K. Goulianos


Diffractive dis @ hera

jet

p

x

x,t

IP

p

g*

e

g*

Q2

e

reorganize

Brodsky et al. rescattering?

Diffractive DIS @ HERA

Factorization holds: J. Collins

Pomeron exchange

Color reorganization

Twenty Years of Diffraction at the Tevatron K. Goulianos


Inclusive vs diffractive dis

aP(0)-1

eg=0.20

(eq+l)/2

eq=0. 04

eR=-0.5

eq

Inclusive vs Diffractive DIS

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

F2 ~ x-l

Twenty Years of Diffraction at the Tevatron K. Goulianos


Diffractive dijets @ tevatron

jet

p

jet

reorganize

Diffractive Dijets @ Tevatron

Twenty Years of Diffraction at the Tevatron K. Goulianos


F d jj x b q 2 @ tevatron

FDJJ(x,b,Q2) @ Tevatron

Twenty Years of Diffraction at the Tevatron K. Goulianos


Sd nd dijet ratio vs x bj @ cdf

SD/ND Dijet Ratio vs xBj@ CDF

0.035 < x < 0.095

Flat x dependence

Twenty Years of Diffraction at the Tevatron K. Goulianos


Restoring factorization @ tevatron

R(SD/ND)

R(DPE/SD)

Restoring Factorization @ Tevatron

DSF from two/one gap:

factorization restored!

Twenty Years of Diffraction at the Tevatron K. Goulianos


Gap between jets

Gap Between Jets

Twenty Years of Diffraction at the Tevatron K. Goulianos


Gap between jets1

Question

Gap Between Jets

Is the diffractive exchange BFKL-like

or simply a color rearrangement?

Twenty Years of Diffraction at the Tevatron K. Goulianos


Low x and diffraction

p

p

valence quarks

antiproton

antiproton

SOFT

HARD

eg=0.20

lg=0.5

eq=0. 04

lq=0.3

eR=-0.5

Low-x and Diffraction

deep sea

valence quarks

Derive diffractive

from inclusive PDFs

and color factors

x=x

proton

Twenty Years of Diffraction at the Tevatron K. Goulianos


Run 2 cdf diffractive program

Run 2 CDF Diffractive Program

  • Single Diffraction

    • x and Q2 dependence of FjjD

    • Process dependence of FD (W, J/y)

  • Double Diffraction

    • Jet-Gap-Jet: Dhgap for fixed large Dhjet

  • Double Pomeron Exchange

    • FjjD on p-side vs x-pbar

      Also:

      Exclusive central production

    • Dijets, cc

      Other

    • Tev4LHC issues

Twenty Years of Diffraction at the Tevatron K. Goulianos


Summary

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.

Twenty Years of Diffraction at the Tevatron K. Goulianos


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