23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland1 Konstantin Goulianos The Rockefeller University & The CDF Collaboration Xth Blois Workshop on Elastic and Diffractive Scattering June 2003, Helsinki, Finland Soft and Hard Diffraction at CDF

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion2 Introduction What is hadronic diffraction? X Diffraction dissociation KG, Phys. Rep. 101 (1983) 171 coherence

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland3  Non-diffractive interactions:  Diffractive interactions: rapidity gaps are regions of rapidity devoid of particles Gaps are exponentially suppressed From Poisson statistics: ( r =particle density in rapidity space) large rapidity gaps are signatures for diffraction rapidity gaps are formed by multiplicity fluctuations rapidity gaps, like diamonds, ‘live for ever’ Diffraction and Rapidity Gaps

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland4  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 Pomeron

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland5  Elastic scattering  Total cross section  Diffraction PRD PRL PRL PRL 50 (1994) (2001) to be sub’d accepted SOFT diffraction HARD diffraction Control sample W 78 (1997) 2698JJ 74 (1995) 855JJ 85 (2000) 4217 JJ 79 (1997) 2636JJ 80 (1998) 1156 b-quark 84 (2000) 232JJ 81 (1998) 5278 J/  87 (2001) JJ 84 (2000) 5043 JJ 88 (2002) with roman pots PRL reference PRD 50 (1994) 5518 PRD 50 (1994) 5550 Diffraction at CDF in Run I

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion6 Factorization & (re)normalization Soft diffraction Renormalize to unity KG, PLB 358 (1995) 379 Gap probability  COLOR FACTOR Pomeron trajectory parton model

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland7 Total cross section KG, PLB 358 (1995) 379 Differential cross section KG&JM, PRD 59 (114017) 1999 REGGE RENORM s-independent  Differential shape agrees with Regge  Normalization is suppressed by factor ~  Renormalize Pomeron flux factor to unity M 2 SCALING Soft Single Diffraction Data

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland8  Double diffraction  Plot #Events versus   Double Pomeron Exchange  Measure  Plot #Events versus log(  )  SDD: single+double diffraction  Central gaps in SD events Central and Double Gaps

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland9 color factor 5 independent variables Gap probability Sub-energy cross section (for regions with particles) Integral Renormalization removes the s-dependence SCALING Two-Gap Diffraction (hep-ph/ )

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland10 Differential shapes agree with Regge predictions  One-gap cross sections require renormalization DDSDDDPE  Two-gap/one-gap ratios are Central and Double-Gap Results

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland11 Soft Double Pomeron Exchange  Roman Pot triggered events  <  -pbar < |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!)

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion12 Hard diffraction in Run I BBC 3.2<  <5.9 FCAL 2.4<  <4.2 BBC FCAL Diffractive dijets CDF Forward Detectors

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland13  SINGLE DIFFRACTION  DOUBLE DIFFRACTION 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 GeVDD/ND gap fraction at 1800 GeV All SD/ND fractions ~1% Gluon fraction Suppression by ~5 relative to HERA Just like in ND except for the suppression due to gap formation Hard Diffraction Using Rapidity Gaps

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland14 ISSUES: 1) QCD factorization > is F SD universal? 2) Regge factorization > (not detected) Bjorken-x of antiproton Nucleon structure function Diffractive structure function ? momentum fraction of parton in IP METHOD of measuring F SD : measure ratio R( ,t) of SD/ND rates for given ,t set R( ,t)=F SD /F ND evaluate F SD = R * F ND Diffractive Dijets with Leading Antiproton The diffractive structure function

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland15 Test Regge factorization Test QCD factorization Regge factorization holdsSuppressed at the Tevatron relative to predictions based on HERA parton densities !!! Dijets in Single Diffraction

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland16 (not detected) R(SD/ND) R(DPE/SD) Test of factorization equal? Factorization breaks down The second gap is un-suppressed!!! Dijets in Double Pomeron Exchange

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion17 Run II Diffraction at the Tevatron CDF Forward Detectors MiniPlug calorimeters (3.5<  <5.5) Beam Shower Counters (5.5<  <7.5) Antiproton Roman Pot Spectrometer

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland18 Run II Forward Detector Layout

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland19 MiniPlug Run II Data ADC counts in MiniPlug towers in a pbar-p event at 1960 GeV. “jet” indicates an energy cluster and may be just a hadron. Approximately 1000 counts = 1 GeV Multiplicity distribution in SD and ND events MiniPlug tower structure

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland20 J5At least one cal tower with ET > 5 GeV RP inclusiveThree-fold coincidence in RP trigger counters RP+J5Single Diffractive dijet candidates RP+J5+BSC-GAP_pDouble 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: (-)+ is for (anti)proton Run II Data Samples

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland21 Diffractive Dijet Sample ND+SD & SD+MB overlap events  ~ 1 SD events 0.03<  <0.1 Flat region

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland22 Diffractive Dijet Structure Function Ratio of SD to ND dijet eventrates as a function of x Bj for different values of Q 2 =ET 2 Ratio of SD to ND dijet event rates as a function of x Bj 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

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland23 Dijets in DPE In SD data with RP+J5 trigger select events with rapidity gap in both the BSC_p and MP_p (3.5 <  <7.5)

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland24 Data Selection DPE dijet candidatesDPE: RP+J5+BSC_GAP_p Single Diffractive dijet candidatesSD: RP+J5 Tower with ET > 5 GeV ND: J5 Prescale=5 Prescale=280

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland25 DPE Dijet Kinematics

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland26 Inclusive/Exclusive DPE Dijet Predictions

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland27 Limit on Exclusive DPE Dijets (Run I) Observed ~100 DPE dijet events  <  <  Jet E T > 7 GeV  Rapidity gap in 2.4 <  < 5.9 Dijet mass fraction M JJ based on energy within cone of 0.7 => look for exclusive dijets in window 0.7 < R JJ < 0.9

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland28 Run II: Exclusive DPE Dijets ? No exclusive dijet bump observed

23-28 June 2003K. Goulianos, Blois Workshop, Helsinki, Finland29 Double Pomeron Exchange Dijet Events Rjj=0.81, Jet1(2)=33.4(31.5) GeVRjj=0.36, Jet1(2)=36.2(33.3) GeV

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion30 SUMMARY Soft and hard conclusions b Soft Diffraction e Hard Diffraction  Pay a color factor  for each gap Use the reduced energy cross section Get gap size from renormalized P gap Diffraction is an interaction between low-x partons subject to color constraints