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Aspects of Diffraction at CDF

Aspects of Diffraction at CDF. 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. Introduction. X. What is hadronic diffraction?. Diffraction dissociation.

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Aspects of Diffraction at CDF

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  1. Aspects of Diffraction at CDF 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 K. Goulianos, Low-x Workshop, Nafplion

  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, Low-x Workshop, Nafplion

  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, Low-x Workshop, Nafplion

  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 submitted HARD diffraction PRL reference with roman pots K. Goulianos, Low-x Workshop, Nafplion

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

  7. Reggeons Key players: • Both rise at small x • but integral does not fit data; • M2-dependence of IP-IP-R • does not fit low-s data; • => KG: Renormalize IP-IP-IP • Reggeon contribution: • important at large x KG & JM: use renormalized IP-IP-IP plus p-p-IP with only g IP-IP-IP as free parameter K. Goulianos, Low-x Workshop, Nafplion

  8. 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, Low-x Workshop, Nafplion

  9. 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 GeV2 corrected for acceptance KG&JM, PRD 59 (114017) 1999 K. Goulianos, Low-x Workshop, Nafplion

  10. 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, Low-x Workshop, Nafplion

  11. 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, Low-x Workshop, Nafplion

  12. Soft Double Pomeron Exchange K. Goulianos, Low-x Workshop, Nafplion

  13. Two-Gap Diffraction (hep-ph/0205141) 7 independent variables color factor Gap probability Sub-energy cross section (for regions with particles) Integral Renormalization removes the s-dependence SCALING K. Goulianos, Low-x Workshop, Nafplion

  14. Multigap Diffraction (hep-ph/0205141) Renormalize gap probability to calculate multigap cross sections Amplitude 5 region-centers Vi 10 variables 1 sum of all gaps 4 t-values one k factor for each gap Use amplitude at t=0 for x-section Use amplitude squared for gaps form factors Pgap depends on sum of gaps Renormalize: set integral of Pgap to unity K. Goulianos, Low-x Workshop, Nafplion

  15. 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

  16. 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, Low-x Workshop, Nafplion

  17. (not detected) Diffractive Dijets with Leading Antiproton 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, Low-x Workshop, Nafplion

  18. 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, Low-x Workshop, Nafplion

  19. (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, Low-x Workshop, Nafplion

  20. 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

  21. Run II Forward Detector Layout K. Goulianos, Low-x Workshop, Nafplion

  22. 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, Low-x Workshop, Nafplion

  23. 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, Low-x Workshop, Nafplion

  24. ND+SD & SD+MB overlap events x ~ 1 SD events 0.03<x<0.1 Flat region Diffractive Dijet Sample K. Goulianos, Low-x Workshop, Nafplion

  25. 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, Low-x Workshop, Nafplion

  26. 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, Low-x Workshop, Nafplion

  27. 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, Low-x Workshop, Nafplion

  28. DPE Dijet Kinematics K. Goulianos, Low-x Workshop, Nafplion

  29. Inclusive/Exclusive DPE Dijet Predictions K. Goulianos, Low-x Workshop, Nafplion

  30. 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, Low-x Workshop, Nafplion

  31. Run II: Exclusive DPE Dijets ? No exclusive dijet bump observed K. Goulianos, Low-x Workshop, Nafplion

  32. 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, Low-x Workshop, Nafplion

  33. 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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