4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion1 Konstantin Goulianos The Rockefeller University & The CDF Collaboration Low-x Workshop, Nafplion, Greece, 4-7 June 2003 Introduction Run I review Run II results Conclusion Aspects of 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion3  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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion4  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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion5  Elastic scattering  Total cross section  Diffraction PRD PRL PRL PRL 50 (1994) (2001) to be sub’d submitted 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 & Renormalization Soft diffraction Renormalize to unity KG, PLB 358(1995)379 Gap probability  COLOR FACTOR Pomeron trajectory parton model

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion7 Reggeons Key players: Both rise at small  but integral does not fit data; M 2 -dependence of IP-IP-R does not fit low-s data; => KG: Renormalize IP-IP-IP Reggeon contribution: important at large  KG & JM: use renormalized IP-IP-IP plus  -IP with only g IP-IP-IP as free parameter

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion8 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion9 CDF Single Diffraction Data and Fits Data versus MC based on triple-Pomeron plus Reggeon CDF PRD 50 (1994) 5535 Data at |t|=0.05 GeV 2 corrected for acceptance KG&JM, PRD 59 (114017) 1999

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion10  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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion11 Differential shapes agree with Regge predictions  One-gap cross sections require renormalization DDSDDDPE  Two-gap/one-gap ratios are Central and Double-Gap Results

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion12 Soft Double Pomeron Exchange

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion13 color factor 7 independent variables Gap probability Sub-energy cross section (for regions with particles) Integral Renormalization removes the s-dependence SCALING Two-Gap Diffraction (hep-ph/ )

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion14 5 region-centers 1 sum of all gaps 4 t-values V i 10 variables Renormalize gap probability to calculate multigap cross sections Use amplitude at t=0 for x-section Use amplitude squared for gaps P gap depends on sum of gaps form factors Renormalize: set integral of P gap to unity Amplitude one  factor for each gap Multigap Diffraction (hep-ph/ )

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion15 Hard diffraction in Run I BBC 3.2<  <5.9 FCAL 2.4<  <4.2 BBC FCAL Diffractive dijets CDF Forward Detectors

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion16  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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion17 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion18 Test Regge factorization Test QCD factorization Regge factorization holdsSuppressed at the Tevatron relative to predictions based on HERA parton densities !!! Dijets in Single Diffraction

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion19 (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, Nafplion20 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion21 Run II Forward Detector Layout

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion22 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion23 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion24 Diffractive Dijet Sample ND+SD & SD+MB overlap events  ~ 1 SD events 0.03<  <0.1 Flat region

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion25 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion26 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)

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion27 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion28 DPE Dijet Kinematics

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion29 Inclusive/Exclusive DPE Dijet Predictions

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion30 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

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion31 Run II: Exclusive DPE Dijets ? No exclusive dijet bump observed

4-7 June 2003K. Goulianos, Low-x Workshop, Nafplion32 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, Nafplion33 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