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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos1 Diffraction: from HERA & Tevatron to LHC K. Goulianos, The Rockefeller University DIFFRACTION AT THE LHC RIO DE JANEIRO, BRAZIL, 31 March – 2 April 2004
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos2 Diffractive signatures Leading hadron(s) Rapidity gap(s)
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos3 Leading hadrons X Diffraction dissociation KG, Phys. Rep. 101 (1983) 171
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos4 Rapidity gaps Minimum bias Diffraction dissociation Gaps exponentially suppressed From Poisson statistics: MXMX gap
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos5 QCD aspects of diffraction Quark/gluon exchange across a rapidity gap: POMERON No particles radiated in the gap: the exchange is COLOR-SINGLET with vacuum quantum numbers Rapidity gap formation: NON-PERTURBATIVE Diffraction probes the large distance aspects of QCD: POMERON CONFINEMENT PARTONIC STRUCTURE FACTORIZATION PROPERTIES ? MXMX gap
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos6 History of Diffraction 1960Good and Walker 1960’sBNL: first observation 1970’sFermilab fixed target, ISR, SPS 1983KG, Phys. Rep. 101, 169 (1983) 1992UA8: diffractive dijets hard diff 1993-2003Golden decade: HERA, Tevatron, RHIC 40 years of diffraction
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos7 SOFT DIFFRACTION Soft and Hard Diffraction HARD DIFFRACTION = P L /P L =fractional momentum loss of scattered (anti)proton Variables: ( , t) or ( , t) Additional variables: (x, Q 2 ) dN/d MXMX =-ln t dN/d ln M X 2
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos8 Breakdown of QCD factorization dN/d gap e ** HERA TEVATRON dN/d gap pp IP t CDF H1 pp IP p ???
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos9 Diffractive vs inclusive structure fn’s F 2 D (x,Q 2 ) /F 2 (x,Q 2 ) F D JJ (x,Q 2 ) /F(x,Q 2 ) ~ no Q 2 dependence ~ flat at HERA ~ 1/ x 0.5 at Tevatron
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos10 CDF Run I results
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos11 Unitarity problem: With factorization and std pomeron flux SD exceeds T at Renormalization: normalize the pomeron flux to unity Soft Diffraction MXMX KG, PLB 358 (1995) 379 ~10
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos12 A Scaling Law in Diffraction KG&JM, PRD 59 (1999) 114017 Factorization breaks down in favor of M 2 -scaling renormalization 1
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos13 Double Diffraction Dissociation One central gap Double Pomeron Exchange Two forward gaps SDD: Single+Double Diffraction Forward + central gaps Central and Double Gaps
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos14 Elastic & total
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos15 2 independent variables: Gap probability Renormalization removes the s-dependence SCALING Generalized renormalization (KG, hep-ph/0205141) color factor t
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos16 The factors and Experimentally: Color factor: KG&JM, PRD 59 (114017) 1999 g =0.20 q =0.04 R =-0.5 Intercept: w g =gluon fraction w q =quark fraction
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos17 color factor 5 independent variables Gap probabilitySub-energy cross section (for regions with particles) Two-Gap Diffraction (KG, hep-ph/0205141) Same suppression as for single gap!
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos18 Differential shapes agree with Regge predictions One-gap cross sections are suppressed DDSDDDPE Two-gap/one-gap ratios are Central & Double-Gap Results
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos19 Soft Double Pomeron Exchange Roman Pot triggered events 0.035 < -pbar < 0.095 |t-pbar| < 1 GeV 2 -proton measured using Data compared to MC based on Pomeron exchange with Pomeron intercept =0.1 Good agreement over 4 orders of magnitude!
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos20 Soft gap survival probability S =
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos21 Hard Diffraction & QCD 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. ~10 Factorization Breakdown Diffractive structure function HERA Tevatron
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos22 Double-Gap Hard Diffraction @TEV vs HERA R(SD/ND)R(DPE/SD) DSF from double-gapsDSF from single-gaps
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos23 Diffractive structure function from inclusive pdf’s (KG) Power-law region max = 0.1 x max = 0.1 < 0.05 g =0.20 q =0. 04 R =-0.5 g =0.5 q =0.3
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos24 Pomeron Intercept from H1 RENORM 1+
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos25 Pomeron intercept from ZEUS
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos26 Gap between jets Question
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos27 Exclusive Dijets in DPE Interest in diffractive Higgs production Calibrate on exclusive dijets Dijet mass fraction Upper limit for excl DPE-jj consistent with theory no peak!
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos28 Exclusive c Production in DPE Cross section upper limit comparable to KMR prediction
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos29 Summary M 2 – scaling Non-suppressed double-gap to single-gap ratios Flavor-independence SD/ND ratio Get diffractive from non-diffractive pdf’s SOFT DIFFRACTION Universality of gap prob. across soft and hard diffraction HARD DIFFRACTION
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Brazil 31 Mar – 2 Apr 2004 Diffraction: from HERA & Tevatron to LHC K. Goulianos30 HERA &Tevatron->LHC p IP
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