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Diffractive x-sections and event final states at the LHC Konstantin Goulianos The Rockefeller University http://physics.rockefeller.edu / Diffraction Day 7 May 2010 CERN
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 2 Describe a phenomenology based on pre-LHC results and use it to: make predictions for LHC suggest measurements to confirm / modify parameters suggest scheme to be implemented in MC simulations propose method to measure luminosity Current MC generators: unreliable for extrapolations to LHC MC tuning based on multi-parameter tuning of ill-defined event topologies Solution: use nested x-sections Contents define diffractive x-section event topologies nested diffractive gaps describe in terms of proton pdf’’s and QCD color factors normalize to guarantee unitarity renormalization model OUTLINE
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 3 REMARKS MC generators inadequate: e.g. PYTHIA and PHOJET predictions of diffractive processes disagree with each other and with data. Diffractive factorization at HERA? Breakdown observed in, e.g. Vector mesons: vs. W, b-slopes of t-distributions Dijets: E T jet dependence, resolved vs. direct components,... RENORM model: describes both p(pbar)-p and p Luminosity measurement: requires a known x-section suggest SD – well defined and slowly varying
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 4 Diffractive pp(pp) processes @ CDF Single Diffraction dissociation (SD) Double Diffraction dissociation (DD) Double Pomeron Exchange (DPE) Central Diffraction Single + Double Diffraction (SDD) SD SDD Elastic scatteringTotal cross section T =Im f el (t=0) OPTICAL THEOREM gap nested gap Use nesting until no diffractive gap fits in √s'
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 5 Definitions dN/d M p p’ rap-gap =-ln 0 p M ,t,t p p p’ ln M 2 ln s particles M 2 scaling: no price paid for increasing diffractive gap size
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 6 M 2 scaling KG&JM, PRD 59 (1999) 114017 factorization breaks down to ensure M 2 scaling - why? Regge 1 Independent of s over 6 orders of magnitude in M 2 ! d dM 2 | t=-0.05 independent of s over 6 orders of magnitude ! data
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 7 T SD (pp & pp) Factor of ~8 (~5) suppression at √s = 1800 (540) GeV suppressed relative to Regge KG, PLB 358, 379 (1995) 1800 GeV 540 GeV M ,t,t p p p’ T SD mb √s=22 GeV
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 8 Gap probability MUST be normalized to unity! Single Diffraction 2 independent variables: t color factor gap probability sub-energy x-section
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 9 Single diffraction (re)normalized Pumplin bound obeyed at all impact parameters Grows slower than s
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 10 Unitarity and Renormalization Two free parameters: s 0 and g PPP Obtain product g PPP s 0 from SD Renormalized Pomeron flux determines s 0 Get unique solution for g PPP Pomeron-proton x-section Pomeron flux gap probability Set to unity – determines g PPP and s 0 KG, PLB 358 (1995) 379
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 11 Dijets in p at HERA from RENORM Factor of ~3 suppression expected at W~200 GeV (just as in pp collisions) for both direct and resolved components K. Goulianos, POS (DIFF2006) 055 (p. 8)
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 12 Multi-gap Diffraction (KG, hep-ph/0205141) y
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 13 Multi-gap Cross Sections Same suppression as for single gap! Gap probabilitySub-energy cross section (for regions with particles) 5 independent variables color factor
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 14 Rapidity Gaps in Fireworks
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 15 Gap survival probability S =
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 16 Diffractive Structure Function CDF H1 momentum fraction of parton in “Pomeron” – note quotes Using preliminary pdf’s from same suppression as in soft diffraction – why? Breakdown of QCD factorization
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 17 Diffractive dijets @ Tevatron p jet reorganize jet
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 18 F D JJ ( , Q 2 ) @ Tevatron
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 19 SD/ND dijet ratio vs. x Bj @ CDF 0.035 < < 0.095 Flat dependence for < 0.5 CDF Run I
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 20 Diffractive DIS @ HERA e Q2Q2 ** p jet reorganize J. Collins: factorization holds (but under what conditions?) e ** t p IP Pomeron exchangeColor reorganization Results favor color reorganization
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 21 Dijets in p at HERA - 2008 DIS 2008 talk by W. Slomiński, ZEUS 20-50 % apparent rise when E T jet 5 10 GeV due to suppression at low E T jet !!!
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 22 Vector meson production (Pierre Marage, HERA-LHC 2008) left - why different vs. W slopes? more room for particles right - why smaller b-slope in *p? same reason
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 23 Unexpected, not understood QCD factorisation not OK Dijets in p at HERA – 2007 Hadron-like e Q2Q2 ** p jet reorganize Direct vs. resolved the reorganization diagram predicts: suppression at low Z | P jets, since larger is available for particles same suppression for direct and resolved processes
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 24 SD and ratio of '
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 25 The total x-section √s F =22 GeV SUPERBALL MODEL
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K. Goulianos D-day 7 May 2010 CERNDiffractive x-sections and event final states at the LHC 26 Strategy and Conclusion T from SUPERBALL model optical theorem Im f el ( t=0 ) dispersion relations Re f el ( t=0 ) differential SD from RENORM use nested pp multiplicities for pomeron-proton collisions at √s‘ For a phenomenological approach see: K. Goulianos, Phys. Lett. B 193 (1987) 151 pp T optical theorem Im f el (t=0) dispersion relations Re f el (t=0) STRATEGY CONCUSION more to come…
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