K. Goulianos The Rockefeller University EDS May 2005 Chateau de Blois, France Twenty Years of Diffraction at the Tevatron

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos2 - p Interactions Diffractive: vacuum exchange Protons retain their quantum numbers Non-diffractive: color exchange Protons acquire color and break apart

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos3 Why Study Particle Diffraction?

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos4 Asymmetric Fireworks? Po’< Po

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos5 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, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos6 1960’sBNL: first observation of pp -> pX 1970’sFermilab fixed target, ISR, SPS  Regge theory & factorization Review: KG, Phys. Rep. 101 (1983) ’sUA8: diffractive dijets  hard diffraction 1990’sTev Run-I: Regge factorization breakdown Tev vs HERA: QCD factorization breakdown 21 st C Multigap diffraction: restoration of factorization Ideal for diffractive LHC Forty Years of Diffraction Twenty Years at the Tevatron

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos7 CDF Run 1-0 ( ) Elastic, single diffractive, and total cross 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  ’ ln s ]  shrinking forward peak  Single diffraction Breakdown of Regge factorization Additional Detectors Trackers up to |  | = 7

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos8 Run 1-0 results in perspective KG, PLB 358 (1995) 379

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos9 CDF Run 1 ( ) Run-IC Run-IA,B Forward Detectors BBC 3.2<  <5.9 FCAL 2.4<  <4.2

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos10 CDF in Run I 93(2004)141601

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos11 All ratios ~ 1%  ~ uniform suppression ~ FACTORIZATION Diffractive CDF 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 ratio at 1800 GeV

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos12 Tevatron vs HERA: Breakdown of QCD Factorization CDF H1

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos13 Multigap Diffraction (KG, hep-ph/ )  y

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos14 Elastic and Total Cross Sections QCD expectations y  Elastic cross section: forward scattering amplitude The exponential rise of  T (  y’) is due to the increase of wee partons with  y’ (see E. Levin, An Introduction to Pomerons,Preprint DESY ) y  Total cross section: power law rise with energy  s

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos15 Gap probability MUST be normalized to unity! Single Diffraction 2 independent variables: t color factor gap probability sub-energy x-section

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos16 Single diffraction (re)normalized  No unitarity problem after eikonalization of the elastic amplitude Grows slower than ln s

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos17 Total Single Diffractive x-Section  Unitarity problem: Using factorization and std pomeron flux  SD exceeds  T at  Renormalization: Normalize the Pomeron flux to unity KG, PLB 358 (1995) 379

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos18 The Factors  and  Experimentally: KG&JM, PRD 59 (114017) 1999 g =0.20 q =0.04 R =-0.5 f g =gluon fraction f q =quark fraction Color factor: Pomeron intercept: CTEQ5L

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos19 Multigap Cross Sections Same suppression as for single gap! Gap probabilitySub-energy cross section (for regions with particles) 5 independent variables color factors

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos20 Central and Two-Gap CDF Results  One-gap cross sections are suppressed  Two-gap/one-gap ratios are Agreement with renormalized Regge predictions DDSDDDP E

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos21 Gap Survival Probability S = Results similar to predictions by: Gotsman-Levin-Maor Kaidalov-Khoze-Martin-Ryskin Soft color interactions

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos22 Diffractive HERA e Q2Q2 ** p jet  reorganize Factorization holds: J. Collins e **  t p IP Pomeron exchangeColor reorganization Brodsky et al. rescattering?

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos23 Inclusive vs Diffractive DIS  P (0)-1 (  q  )/2 F 2 ~ x  qq  g =0.20  q =0. 04  R =-0.5 KG, “Diffraction: a New Approach,” J.Phys.G26: ,2000 e-Print Archive: hep-ph/

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos24 Diffractive Tevatron p jet reorganize jet

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos25 F D JJ ( , Q 2 Tevatron

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos26 SD/ND Dijet Ratio vs x CDF <  < Flat  dependence

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos27 Restoring Tevatron R(SD/ND) R(DPE/SD) DSF from two/one gap: factorization restored!

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos28 Gap Between Jets

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos29 Gap Between Jets Question Is the diffractive exchange BFKL-like or simply a color rearrangement?

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos30 valence quarks antiproton x=x= Low-x and Diffraction proton  g =0.20  q =0. 04  R =-0.5 g =0.5 q =0.3 SOFTHARD deep sea Derive diffractive from inclusive PDFs and color factors antiproton valence quarks p p

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos31 Run 2 CDF Diffractive Program  Single Diffraction   and Q 2 dependence of F jj D  Process dependence of F D (W, J/   Double Diffraction  Jet-Gap-Jet:  gap for fixed large  jet  Double Pomeron Exchange  F jj D on p-side vs  -pbar Also: Exclusive central production  Dijets,  c Other  Tev4LHC issues

EDS 2005, May 2005Twenty Years of Diffraction at the Tevatron K. Goulianos32 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.