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Diffraction from HERA and Tevatron to LHC

Diffraction from HERA and Tevatron to LHC. Konstantin Goulianos The Rockefeller University. Workshop on physics with forward proton taggers at the Tevatron and LHC 14-16 December 2003, Manchester, UK. results theory predictions. Topics. Soft diffraction

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Diffraction from HERA and Tevatron to LHC

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  1. Diffraction from HERA and Tevatron to LHC Konstantin Goulianos The Rockefeller University Workshop on physics with forward proton taggers at the Tevatron and LHC 14-16 December 2003, Manchester, UK • results • theory • predictions K. Goulianos

  2. Topics • Soft diffraction • Elastic and total cross sections • M2-scaling • Soft diffraction cross sections • Multigap diffraction • Diffractive DIS at HERA • Derive F2D3 • Explain flat ratio of F2D3 / F2 • Explain rise of e ( or aIP) with Q2 • Hard diffraction at the Tevatron • Explain ratio of Fjj(SD) / Fjj(ND) – magnitude and shape! • Double-gap hard diffraction • Diffraction at the LHC • Soft and hard single and multigap diffraction • Determine: • triple-pomeron coupling • pomeron intercept • diffractive cross section • using soft parton densities Predict from hard plus soft parton densities K. Goulianos

  3. Diffraction at CDF in Run I 16 papers 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 submitted 91(2003)011802 HARD diffraction PRL reference with roman pots K. Goulianos

  4. Two (most) important results Soft Diffraction Hard Diffraction M2SCALING POWER LAW KG&JM, PRD 59 (1999) 114017 CDF, PRL 84 (2000) 5043 K. Goulianos

  5. 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 4 orders of magnitude! K. Goulianos

  6. Total Cross Section • st exhibits universal rise with energy • the falling term at low energies has NOTHING to do with this rise! • POWER LAW behavior: t=0 elastic scattering amplitude Parton model: # of wee partons grows exponentially K. Goulianos

  7. SOFT DIFFRACTION HARD DIFFRACTION dN/dh dN/dh Dh=-lnx h t Single Diffraction Variables x=DPL/PL fractional momentum loss of scattered hadron Additional variables: (x, Q2) Variables: (x, t) or (Dh, t) K. Goulianos

  8. Soft Single Diffraction Phenomenology f COLOR FACTOR Factorization & (re)normalization Gap probability: Normalize to unity KG, PLB 358 (1995) 379 K. Goulianos

  9. The factors k and e Experimentally: KG&JM, PRD 59 (114017) 1999 Theoretically: lg=0.20 lq=0.04 lR=-0.5 K. Goulianos

  10. Soft Single Diffraction Data Total cross section KG, PLB 358 (1995) 379 Differential cross section KG&JM, PRD 59 (114017) 1999 Regge REGGE RENORM s-independent • Differential shape agrees with Regge • Normalization is suppressed by factor • Renormalize Pomeron flux factor to unity M2 SCALING K. Goulianos

  11. Central and Double Gaps • Double Diffraction Dissociation • One central gap • Double Pomeron Exchange • Two forward gaps • SDD: Single+Double Diffraction • Forward + central gaps K. Goulianos

  12. 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

  13. Central and Double-Gap CDF Results Differential shapes agree with Regge predictions DD SDD DPE • One-gap cross sections require renormalization • Two-gap/one-gap ratios are K. Goulianos

  14. Soft Diffraction Summary Multigap variablesParton model amplitude rapidity gap regions color factor = 0.17 particle cluster regions also: t-across gap centers of floating gap/clusters Differential cross section Normalized gap probability Sub-energy cross section form factor for surviving nucleon color factor: one k for each gap K. Goulianos

  15. F2(x,Q2) = c x-l enter HERA [from the talk of E. Tassi @ Small-x and Diffraction 2003, Fermilab] l(Q2) versus Q2 F2 from Compton analysis (H1) K. Goulianos

  16. lg=0.5 lq=0.3 Diffractive DIS @ HERA eg=0.20 Power-law region xmax = 0.1 xmax = 0.1 b < 0.05x eq=0. 04 eR=-0.5 K. Goulianos

  17. F2D3(xIP,x,Q2)/F2(x,Q2) At fixed xIP: F2D3(xIP ,x,Q2)evolves asF2(x,Q2) independent of the value of x K. Goulianos

  18. 1+(e+l)/2 Pomeron Intercept in DDIS 1+l K. Goulianos

  19. H1-2002 Regge factorization holds Diffractive Dijets @Tevatron Test Regge factorization Test QCD factorization suppressed at the Tevatron relative to extrapolations from HERA parton densities K. Goulianos

  20. Rjj(x) @Tevatron K. Goulianos

  21. lg=0.5 lq=0.3 Rjj=FjjSD/FjjND eg=0.20 Power-law region xmax = 0.1 b < 0.05x eq=0. 04 eR=-0.5 K. Goulianos

  22. RENORM prediction of R(x) vs data CDF data R(x) • Ratio of diffractive to non-diffractive structure functions is predicted from PDF’s and color factors with no free parameters. Fjj(b,x) correctly predicted • Test: processes sensitive to quarks will have more flat R(x) – diff W? RENORM prediction exp-syst-errors K. Goulianos

  23. RENORM PREDICTIONS HERATevatronTev/HERA (e+l)_effective -- 0.55 -- Normalization 0.76 0.042 0.06 R(x)=FD(x)/F(x) flat x-(e+l)_eff ~ x-0.5 e_eff = [e+l(Q2)]/2 ~ 0.2 -- -- HERA vs Tevatron (re)normalized gap probability Pomeron flux K. Goulianos

  24. Another issue QCD evolution Rjj(xBj) vs Q2 No appreciable ET2 dependence observed within 100 < ET2 < 1600 GeV2 K. Goulianos

  25. Dijets in Double Pomeron Exchange Test of factorization R(SD/ND) equal? R(DPE/SD) (not detected) The second gap is less suppressed!!! Factorization breaks down, butsee next slide! K. Goulianos

  26. DSF: Tevatron double-gaps vs HERA The diffractive structure function derived from double-gap events approximately agrees with expectations from HERA K. Goulianos

  27. SUMMARY • Soft Diffraction Use reduced energy cross section • Pay a color factor kfor 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

  28. Inclusive Diffractive Higgs at the LHC enter LHC p+p p-gap-(H+X)-gap-p sD(LHC) ~ k2 * sND (Tevatron) => (0.17)2 * 1 pb = 30 fb K. Goulianos

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