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HERA and the LHC

HERA and the LHC. Diffractive Gap Probability. K. Goulianos, The Rockefeller University CERN 26-27 March 2004. Diffractive signatures. Leading hadron(s) Rapidity gap(s). X. Leading hadrons. Diffraction dissociation. KG, Phys. Rep. 101 (1983) 171. M X. gap. f. f. h. h.

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HERA and the LHC

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  1. HERA and the LHC Diffractive Gap Probability K. Goulianos, The Rockefeller University CERN 26-27 March 2004 HERA and the LHC: Diffractive Gap Probability K. Goulianos

  2. Diffractive signatures • Leading hadron(s) • Rapidity gap(s) HERA and the LHC: Diffractive Gap Probability K. Goulianos

  3. X Leading hadrons Diffraction dissociation KG, Phys. Rep. 101 (1983) 171 HERA and the LHC: Diffractive Gap Probability K. Goulianos

  4. MX gap f f h h Rapidity gaps • Minimum bias • Diffraction dissociation From Poisson statistics: Gaps exponentially suppressed HERA and the LHC: Diffractive Gap Probability K. Goulianos

  5. ? f gap MX h QCD aspects of diffraction • Quark/gluon exchange across a rapidity gap: POMERON • No particles radiated in the gap: the exchange is COLOR-SINGLETwith vacuum quantum numbers • Rapidity gap formation: NON-PERTURBATIVE • Diffraction probes the large distance aspects of QCD: POMERON CONFINEMENT • PARTONIC STRUCTURE • FACTORIZATION PROPERTIES HERA and the LHC: Diffractive Gap Probability K. Goulianos

  6. History of Diffraction 40 years of diffraction • 1960 Good and Walker • 1960’s BNL: first observation • 1970’s Fermilab fixed target, ISR, SPS • 1983 KG, Phys. Rep. 101, 169 (1983) • 1992 UA8: diffractive dijets a hard diff • 1993-2003 Golden decade: HERA, Tevatron, RHIC HERA and the LHC: Diffractive Gap Probability K. Goulianos

  7. SOFT DIFFRACTION HARD DIFFRACTION MX dN/dh dN/dh Dh=-lnx ln MX2 h t Soft and Hard Diffraction x=DPL/PL x=fractional momentum loss of scattered (anti)proton Additional variables: (x, Q2) Variables: (x, t) or (Dh, t) HERA and the LHC: Diffractive Gap Probability K. Goulianos

  8. IP IP p p p p Breakdown of QCD factorization HERA TEVATRON p x,t IP g* H1 e CDF gap gap dN/dh dN/dh h h XXX HERA and the LHC: Diffractive Gap Probability K. Goulianos

  9. Diffractive vs inclusive structure fn’s FDJJ(x,Q2) /F(x,Q2) F2D(x,Q2) /F2(x,Q2) ~ no Q2 dependence ~ flat at HERA ~ 1/x0.5 at Tevatron HERA and the LHC: Diffractive Gap Probability K. Goulianos

  10. CDF Run I results HERA and the LHC: Diffractive Gap Probability K. Goulianos

  11. MX Soft Diffraction • Unitarity problem: With factorization and std pomeron flux sSD exceeds sT at • Renormalization: normalize the pomeron flux to unity ~10 KG, PLB 358 (1995) 379 HERA and the LHC: Diffractive Gap Probability K. Goulianos

  12. A Scaling Law in Diffraction KG&JM, PRD 59 (1999) 114017 Factorization breaks down in favor of M2-scaling renormalization 1 HERA and the LHC: Diffractive Gap Probability K. Goulianos

  13. Central and Double Gaps • Double Diffraction Dissociation • One central gap • Double Pomeron Exchange • Two forward gaps • SDD: Single+Double Diffraction • Forward + central gaps HERA and the LHC: Diffractive Gap Probability K. Goulianos

  14. f h f h Elastic & total s HERA and the LHC: Diffractive Gap Probability K. Goulianos

  15. color factor Generalized renormalization (KG, hep-ph/0205141) t 2 independent variables: Gap probability Renormalization removes the s-dependence SCALING HERA and the LHC: Diffractive Gap Probability K. Goulianos

  16. lg=0.20 lq=0.04 lR=-0.5 The factors k and e KG&JM, PRD 59 (114017) 1999 Experimentally: Color factor: Intercept: wg=gluon fraction wq=quark fraction HERA and the LHC: Diffractive Gap Probability K. Goulianos

  17. Two-Gap Diffraction (KG, hep-ph/0205141) 5 independent variables color factor Gap probability Sub-energy cross section (for regions with particles) Same suppression as for single gap! HERA and the LHC: Diffractive Gap Probability K. Goulianos

  18. Central & Double-Gap Results Differential shapes agree with Regge predictions DD SDD DPE • One-gap cross sections are suppressed • Two-gap/one-gap ratios are HERA and the LHC: Diffractive Gap Probability K. Goulianos

  19. 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! HERA and the LHC: Diffractive Gap Probability K. Goulianos

  20. S = Soft gap survival probability HERA and the LHC: Diffractive Gap Probability K. Goulianos

  21. ~10 Hard Diffraction & QCD Diffractive structure function • The diffractive structure function measured using SD dijets at the Tevatron is suppressed by about an order of magnitude relative to predictions based on diffractive DIS at HERA • The discrepancy is generally attributed to additional color exchanges which spoil the diffractive rapidity gap. HERA Factorization Breakdown Tevatron HERA and the LHC: Diffractive Gap Probability K. Goulianos

  22. R(SD/ND) R(DPE/SD) DSF from double-gaps DSF from single-gaps Double-Gap Hard Diffraction @TEV vs HERA HERA and the LHC: Diffractive Gap Probability K. Goulianos

  23. lg=0.5 lq=0.3 Diffractive structure functionfrom inclusive pdf’s (KG) eg=0.20 Power-law region xmax = 0.1 xmax = 0.1 b < 0.05x eq=0. 04 eR=-0.5 HERA and the LHC: Diffractive Gap Probability K. Goulianos

  24. RENORM Pomeron Intercept from H1 1+l HERA and the LHC: Diffractive Gap Probability K. Goulianos

  25. Pomeron intercept from ZEUS HERA and the LHC: Diffractive Gap Probability K. Goulianos

  26. Question Gap between jets HERA and the LHC: Diffractive Gap Probability K. Goulianos

  27. Exclusive Dijets in DPE Interest indiffractive Higgs production Calibrate on exclusive dijets Dijet mass fraction no peak! Upper limit for excl DPE-jj consistent with theory HERA and the LHC: Diffractive Gap Probability K. Goulianos

  28. Exclusive cc Production in DPE Cross section upper limit comparable to KMR prediction HERA and the LHC: Diffractive Gap Probability K. Goulianos

  29. Summary SOFT DIFFRACTION • M2 – scaling • Non-suppressed double-gap to single-gap ratios • Flavor-independence SD/ND ratio • Get diffractive from non-diffractive pdf’s HARD DIFFRACTION Universality of gap prob. across soft and hard diffraction HERA and the LHC: Diffractive Gap Probability K. Goulianos

  30. IP p ! Diffraction Soft & Hard HERA &Tevatron->LHC HERA and the LHC: Diffractive Gap Probability K. Goulianos

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