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Diffractive Structure Functions and Exclusive Production from CDF to LHC

Diffractive Structure Functions and Exclusive Production from CDF to LHC. Konstantin Goulianos The Rockefeller University and the CDF Collaboration. Contents. Introduction Elastic and total cross sections Soft diffraction Hard diffraction Exclusive Production.

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Diffractive Structure Functions and Exclusive Production from CDF to LHC

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  1. Diffractive Structure Functionsand Exclusive Production from CDF to LHC Konstantin Goulianos The Rockefeller University and the CDF Collaboration

  2. Contents • Introduction • Elastic and total cross sections • Soft diffraction • Hard diffraction • Exclusive Production Diffraction from CDF to LHCK. Goulianos

  3. Incident hadrons acquire color and break apart POMERON CONFINEMENT p-p Interactions Non-diffractive: Color-exchange Diffractive: Colorless exchange with vacuum quantum numbers rapidity gap Incident hadrons retain their quantum numbers remaining colorless pseudo- DECONFINEMENT Goal: understand the QCD nature of the diffractive exchange Diffraction from CDF to LHCK. Goulianos

  4. Diffractive pp Processes sT=Im fel (t=0) Elastic scattering Total cross section f f OPTICAL THEOREM GAP h h DD DPE SDD=SD+DD SD Diffraction from CDF to LHCK. Goulianos

  5. CDF Run 1-0 (1988-89) Elastic, diffractive, and total cross section @ 546 and 1800 GeV Roman Pot Spectrometers CDF-I • Roman Pot Detectors • Scintillation trigger counters • Wire chamber • Double-sided silicon strip detector Roman Pots with Trackers up to |h| = 7 Diffraction from CDF to LHCK. Goulianos

  6. Run-IC CDF-I Run-IA,B beam Forward Detectors BBC 3.2<h<5.9 FCAL 2.4<h<4.2 Diffraction from CDF to LHCK. Goulianos

  7. ROMAN POT DETECTORS BEAM SHOWER COUNTERS: Used to reject ND events MINIPLUG CALORIMETER CDF-II Diffraction from CDF to LHCK. Goulianos

  8. The MiniPlugs @ CDF Diffraction from CDF to LHCK. Goulianos

  9. ELASTIC AND TOTAL CROSS SECTIONS @ Tevatron: CDF and E710/811  use luminosity independent method  Optical theorem optical theorem • Alert: • background Ninel yields small sT • undetected Ninel yields large sT Diffraction from CDF to LHCK. Goulianos

  10. Total Cross Sections: Regge fit CDF E710 CMG fit: Covolan, Montagna, Goulianos PLB 389 (1995) 176 Born level Simultaneous Regge fit to pp, pp, and Kp x-sections using the eikonal approach to ensure unitarity s  Se e = 1.104 +/- 0.002  sLHC= 115 mb @14 TeV DL Diffraction from CDF to LHCK. Goulianos

  11. Recall CMG Regge fit: 115 mb sT: other approaches eg, M. Block, arXiv:hep-ph/0601210(2006)  fit data using analyticity constraints M. Block and F. Halzen, Phys. Rev. D 72, 036006 • sT (LHC) = 107.3 ± 1.2 mb Diffraction from CDF to LHCK. Goulianos

  12. sT and r-values from PDG r = ratio of real/imaginary parts of elastic scattering amplitude at t=0 CDF CDF and E710/811 disagree E710 E811 sT optical theorem Im fel(t=0) dispersion relations Re fel(t=0) CDF & UA4 E811 N. Khuri and A. Martin: measuring r at the LHC tests discreteness of space-time Diffraction from CDF to LHCK. Goulianos

  13. SOFT DIFFRACTION Key words: renormalization scaling QCD multi-gap Diffraction from CDF to LHCK. Goulianos

  14. Renormalization Factorization  Pomeron flux • Regge theory sSD exceeds sT at • Renormalization Pomeron flux integral (re)normalized to unity KG, PLB 358 (1995) 379 Diffraction from CDF to LHCK. Goulianos

  15. renormalization 1 A Scaling Law in Diffraction KG&JM, PRD 59 (1999) 114017  Independent of S over 6 orders of magnitude in M2 ! Factorization breaks down so as to ensure M2-scaling! Diffraction from CDF to LHCK. Goulianos

  16. f y The QCD Connection Total cross section: power law increase versus s f y ~1/as The exponential rise of sT(Dy’) is due to the increase of wee partons with Dy’ (E. Levin, An Introduction to Pomerons,Preprint DESY 98-120) Elastic cross section: forward scattering amplitude Diffraction from CDF to LHCK. Goulianos

  17. Single Diffraction in QCD (KG, hep-ph/0205141) t 2 independent variables: color factor Gap probability Renormalization removes the s-dependence SCALING Diffraction from CDF to LHCK. Goulianos

  18. 5 independent variables color factors Gap probability Sub-energy cross section (for regions with particles) Same suppression as for single gap! Multi-gap Renormalization (KG, hep-ph/0205141) Diffraction from CDF to LHCK. Goulianos

  19. Central and Double Gaps @ CDF • Double Diffraction Dissociation • One central gap • Double Pomeron Exchange • Two forward gaps • SDD: Single+Double Diffraction • One forward + one central gap Diffraction from CDF to LHCK. Goulianos

  20. Differential shapes agree with Regge predictions DD SDD DPE • One-gap cross sections are suppressed • Two-gap/one-gap ratios are Central & Double-Gap CDF Results Diffraction from CDF to LHCK. Goulianos

  21. S = Gap Survival Probability Results similar to predictions by: Gotsman-Levin-Maor Kaidalov-Khoze-Martin-Ryskin Soft color interactions Diffraction from CDF to LHCK. Goulianos

  22. dN/dh h HARD DIFFRACTION • Diffractive fractions • Diffractive structure function  factorization breakdown • Restoring factorization • Q2 dependence • t dependence • Hard diffraction in QCD JJ, W, b, J/y Diffraction from CDF to LHCK. Goulianos

  23. Diffractive Fractions @ CDF Fraction(%) Fraction: SD/ND ratio at 1800 GeV All ratios ~ 1% ~ uniform suppression ~ FACTORIZATION ! W 1.15 (0.55) JJ 0.75 (0.10) b 0.62 (0.25) J/y 1.45 (0.25) Diffraction from CDF to LHCK. Goulianos

  24. Diffractive Structure Function:Breakdown of QCD Factorization b = momentum fraction of parton in Pomeron The diffractive structure function at the Tevatron is suppressed by a factor of ~10 relative to expectation from pdf’s measured by H1 at HERA Similar suppression factor as in soft diffraction relative to Regge expectations! H1 CDF Using preliminary pdf’s from Diffraction from CDF to LHCK. Goulianos

  25. R(SD/ND) R(DPE/SD) DSF from two/one gap: factorization restored! Restoring QCD Factorization The diffractive structure function measured on the proton side in events with a leading antiproton is NOT suppressed relative to predictions based on DDIS Diffraction from CDF to LHCK. Goulianos

  26. Diffractive Structure Function:Q2 dependence ETjet ~ 100 GeV ! • Small Q2 dependence in region 100 < Q2 < 10,000 GeV2 • Pomeron evolves as the proton! Diffraction from CDF to LHCK. Goulianos

  27. Diffractive Structure Function:t- dependence Fit ds/dt to a double exponential: • No diffraction dips • No Q2 dependence in slope from inclusive to Q2~104 GeV2 • Same slope over entire region of 0 < Q2 < 4,500 GeV2 across soft and hard diffraction! Diffraction from CDF to LHCK. Goulianos

  28. p p valence quarks antiproton antiproton Hard Diffraction in QCD deep sea valence quarks Derive diffractive from inclusive PDFs and color factors x=x proton Diffraction from CDF to LHCK. Goulianos

  29. H EXCLUSIVE PRODUCTION Measure exclusive jj & gg  Calibrate predictions for H production rates @ LHC Bialas, Landshoff, Phys.Lett. B 256,540 (1991) Khoze, Martin, Ryskin, Eur. Phys. J. C23, 311 (2002); C25,391 (2002);C26,229 (2002) C. Royon, hep-ph/0308283 B. Cox, A. Pilkington, PRD 72, 094024 (2005) OTHER………………………… KMR: sH(LHC) ~ 3 fb S/B ~ 1 if DM ~ 1 GeV Clean discovery channel • Search for exclusive gg • 3 candidate events found • 1 (+2/-1) predicted from ExHuME MC* • background under study * See talk by V. Khoze Search for exclusive dijets: Measure dijet mass fraction Look for signal as Mjj 1 Diffraction from CDF to LHCK. Goulianos

  30. Exclusive Dijet Signal Dijet fraction – all jets b-tagged dijet fraction DIJETS Exclusive b-jets are suppressed by JZ= 0 selection rule Excess over MC predictions at large dijet mass fraction Diffraction from CDF to LHCK. Goulianos

  31. RJJ(excl): Data vs MC Exclusive DPE (DPEMC)  non-pQCD based on Regge theory ExHuME (KMR): gggg process  uses LO pQCD Shape of excess of events at high Rjj is well described by both models Diffraction from CDF to LHCK. Goulianos

  32. jjexcl: Exclusive Dijet Signal COMPARISON Inclusive data vs MC @ b/c-jet data vs inclusive Diffraction from CDF to LHCK. Goulianos

  33. JJexcl : x-section vs ET(min) Comparison with hadron level predictions Diffraction from CDF to LHCK. Goulianos

  34. JJexcl : cross section predictions ExHuME Hadron-Level Differential Exclusive Dijet Cross Section vs Dijet Mass (dotted/red):Default ExHuME prediction (points): Derived from CDF Run II Preliminary excl. dijet cross sections Statistical and systematic errors are propagated from measured cross section uncertainties using ExHuME Mjj distribution shapes. Diffraction from CDF to LHCK. Goulianos

  35. Summary TEVATRON – what we have learnt • M2 – scaling • Non-suppressed double-gap to single-gap ratios • Pomeron: composite object made up from underlying pdf’s subject to color constraints LHC - what to do • Elastic and total cross sections & r-value • High mass (4 TeV)and multi-gap diffraction • Exclusive production (FP420 project)  Reduced bgnd for std Higgs to study properties  Discovery channel for certain Higgs scenarios Diffraction from CDF to LHCK. Goulianos

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