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Soft and Hard Diffraction at CDF

Soft and Hard Diffraction at CDF. Konstantin Goulianos The Rockefeller University & The CDF Collaboration. Xth Blois Workshop on Elastic and Diffractive Scattering 23-28 June 2003, Helsinki, Finland. Introduction. X. What is hadronic diffraction?. Diffraction dissociation. coherence.

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Soft and Hard Diffraction at CDF

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

  2. Introduction X What is hadronic diffraction? Diffraction dissociation coherence KG, Phys. Rep. 101 (1983) 171 K. Goulianos, Low-x Workshop, Nafplion

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

  4. ? The Pomeron • Quark/gluon exchange across a rapidity gap: POMERON • No particles radiated in the gap: the exchange is COLOR-SINGLETwith quantum numbers of vacuum • Rapidity gap formation: NON-PERTURBATIVE • Diffraction probes the large distance aspects of QCD: POMERON CONFINEMENT • PARTONIC STRUCTURE • FACTORIZATION K. Goulianos, Blois Workshop, Helsinki, Finland

  5. Diffraction at CDF in Run I PRD 50 (1994) 5518 • Elastic scattering • Total cross section • Diffraction PRD 50 (1994) 5550 SOFT diffraction Control sample PRD PRL PRL PRL 50 (1994) 5535 87 (2001)141802 to be sub’d accepted HARD diffraction PRL reference with roman pots K. Goulianos, Blois Workshop, Helsinki, Finland

  6. Soft diffraction f parton model Factorization & (re)normalization Pomeron trajectory COLOR FACTOR Renormalize to unity KG, PLB 358 (1995) 379 Gap probability K. Goulianos, Low-x Workshop, Nafplion

  7. Soft Single Diffraction Data 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 M2 SCALING K. Goulianos, Blois Workshop, Helsinki, Finland

  8. Central and Double Gaps • Double diffraction • Plot #Events versus Dh • Double Pomeron Exchange • Measure • Plot #Events versus log(x) • SDD: single+double diffraction • Central gaps in SD events K. Goulianos, Blois Workshop, Helsinki, Finland

  9. Two-Gap Diffraction (hep-ph/0205141) 5 independent variables color factor Gap probability Sub-energy cross section (for regions with particles) Integral Renormalization removes the s-dependence SCALING K. Goulianos, Blois Workshop, Helsinki, Finland

  10. Central and Double-Gap Results Differential shapes agree with Regge predictions DD SDD DPE • One-gap cross sections require renormalization • Two-gap/one-gap ratios are K. Goulianos, Blois Workshop, Helsinki, Finland

  11. Soft Double Pomeron Exchange • Roman Pot triggered events • 0.035 < x-pbar < 0.095 |t-pbar| < 1 GeV 2 • x-proton measured using • Data compared to MC based on Pomeron exchange with Pomeron intercept e=0.1 • Good agreement over the entire kinematic region (4 orders of magnitude!) K. Goulianos, Blois Workshop, Helsinki, Finland

  12. Hard diffraction in Run I BBC FCAL CDF Forward Detectors Rapidity gaps Antiproton tag BBC 3.2<h<5.9 FCAL 2.4<h<4.2 Diffractive dijets K. Goulianos, Low-x Workshop, Nafplion

  13. SINGLE DIFFRACTION DOUBLE DIFFRACTION X CDF D0 W 1.15 (0.55) JJ 0.75 (0.10) 0.65 (0.04) b 0.62 (0.25) J/y 1.45 (0.25) Hard Diffraction Using Rapidity Gaps 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 Just like in ND except for the suppression due to gap formation K. Goulianos, Blois Workshop, Helsinki, Finland

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

  15. Dijets in Single Diffraction Test Regge factorization Test QCD factorization Suppressed at the Tevatron relative to predictions based on HERA parton densities Regge factorization holds !!! K. Goulianos, Blois Workshop, Helsinki, Finland

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

  17. Run II Diffraction at the Tevatron CDF Forward Detectors • MiniPlug calorimeters (3.5<h<5.5) • Beam Shower Counters (5.5<h<7.5) • Antiproton Roman Pot Spectrometer K. Goulianos, Low-x Workshop, Nafplion

  18. Run II Forward Detector Layout K. Goulianos, Blois Workshop, Helsinki, Finland

  19. MiniPlug Run II Data MiniPlug tower structure • 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 K. Goulianos, Blois Workshop, Helsinki, Finland

  20. Run II Data Samples Triggers • Results presented are from ~26 pb-1 of data • The Roman Pot tracking system was not operational for these data samples • The x of the (anti)proton was determined from calorimeter information: (-)+ is for (anti)proton K. Goulianos, Blois Workshop, Helsinki, Finland

  21. ND+SD & SD+MB overlap events x ~ 1 SD events 0.03<x<0.1 Flat region Diffractive Dijet Sample K. Goulianos, Blois Workshop, Helsinki, Finland

  22. Diffractive Dijet Structure Function Ratio of SD to ND dijet event rates as a function of xBj compared with Run I data No x dependence observed within 0.03 < x <0.1 (confirms Run I result) Ratio of SD to ND dijet eventrates as a function of xBj for different values of Q2=ET2 No appreciable Q2 dependence observed within 100 < Q2 < 1600 GeV K. Goulianos, Blois Workshop, Helsinki, Finland

  23. 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 < h <7.5) K. Goulianos, Blois Workshop, Helsinki, Finland

  24. DPE: RP+J5+BSC_GAP_p DPE dijet candidates Prescale=5 SD: RP+J5 Single Diffractive dijet candidates Prescale=280 ND: J5 Tower with ET > 5 GeV Data Selection K. Goulianos, Blois Workshop, Helsinki, Finland

  25. DPE Dijet Kinematics K. Goulianos, Blois Workshop, Helsinki, Finland

  26. Inclusive/Exclusive DPE Dijet Predictions K. Goulianos, Blois Workshop, Helsinki, Finland

  27. Limit on Exclusive DPE Dijets (Run I) • Observed ~100 DPE dijet events • 0.035 < x < 0.095 • Jet ET > 7 GeV • Rapidity gap in 2.4 < h < 5.9 Dijet mass fraction MJJ based on energy within cone of 0.7 => look for exclusive dijets in window 0.7 < RJJ < 0.9 K. Goulianos, Blois Workshop, Helsinki, Finland

  28. Run II: Exclusive DPE Dijets ? No exclusive dijet bump observed K. Goulianos, Blois Workshop, Helsinki, Finland

  29. Double Pomeron Exchange Dijet Events Rjj=0.81, Jet1(2)=33.4(31.5) GeV Rjj=0.36, Jet1(2)=36.2(33.3) GeV K. Goulianos, Blois Workshop, Helsinki, Finland

  30. SUMMARY • Soft Diffraction Use the reduced energy cross section • Pay a color factor k for each gap • Hard Diffraction Get gap size from renormalized Pgap Soft and hard conclusions Hard SOFT Diffraction is an interaction between low-x partons subject to color constraints K. Goulianos, Low-x Workshop, Nafplion

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