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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 1 Introduction: QCD at the Tevatron (overview) The High Q^2 Frontier: Jets, tops, W/Z, Q or X? LHC: A new arena for QCD. Detectors Very High Mass Diffraction High Mass “Central Production” (a.k.a. DPE) The FP420 Project

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 2 Recent QCD studies at the Tevatron (CDF & D0) Every interaction is QCD! In May 2003 – May 2005 CDF (D0) published 43 (10) “QCD” papers: other topics to follow...... even that!

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 3 QCD Topics in TeV Publications May 03 – May 05

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 4 Jets Angular (or y) distributions well fit (log scale!)... but y = 2.4 still “central” Below 50 GeV mostly gg (at y=0) Above 400 GeV mostly q-qbar Can study g and q fragmentation At LHC pp p JJ p ~ pure gluons Cone algorithm

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 5 Run 152507 Evt 1222348 All hits/trackstracks pT > 2 GeV/c At the top of the spectrum: 618 GeV 552 GeV CDF kT algorithm

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 6 Here is a beautiful 3-jet event! 155 GeV 402 GeV 444 GeV ET > 0.5 GeV Run/Event 162498/4411694

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 7 Projected Jet Cross Sections at LHC Spectra drawn to few/100GeV bin in 100 fb^-1 Let us hope these are quite wrong: Peak(s), excesses, cut-off (black hole production?) --- the end of high pT physics!

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 8 Coverage in (x,Q2) extended by more than an Order of Magnitude Smallest x requires very forward detectors: * EVENT SHOWN

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 9 Production Cross Sections Rise Strongly with Energy (Except at fixed x) ~ 1 top/sec at 10^33

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 10 BFKL and Mueller-Navelet Jets Color singlet (IP) exchange between quarks Enhancement over 1g exchange – multiRegge gluon ladder Jets with large y separation n minijets in between (inelastic case) large gap in between (elastic case) Fundamental empirical probe of new regime: non-perturbative QCD at short distances. Very forward calorimeters OS

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 11 Berger, Qiu, Wang, hep-ph/0404158 D0 Run II Y-production Cacciari, Frixione, Mangano, Nason, Ridolfi, hep-ph/0312132 CDF B-hadrons Run II CDF, hep-ex/0412071 TeV 03-05

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 12 Penguin diagram TeV 03-05 W

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 13 CDF-7142 Rare Charmless B decays At LHC: LHC-B +ATLAS/CMS?

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 14 pQCD ! TeV 03-05

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 15 Probing Very Small x Gluons High parton densities New phenomena (gluon saturation) HERA measures q(x) to ~ few 10^-5 g(x) by evolution, charm LHC : measure g(x) to < ~ 10^-5 more directly Instrument few degree region with tracking, calorimetry (em+had), muons,, jets, photons... CASTOR, TOTEM

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 16 CDF study: charged particles transverse to high pT jets MPS TeV 03-05

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 17 Beyond Single Parton Distributions Double and multiple parton scattering Hint at ISR (4 “jets”), Seen in UA2 and CDF & Double Drell-Yan : diquarks – anti-diquarks Correlations in b (impact parameter) and x

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 18 But before May 2003: TeV 03-05

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 19 Categories of Diffraction at LHC Can have a 4-unit gap with 2 TeV SD Can have (VF)J – G6 – (VF)J Can have 2 x 3-unit gaps with 700 GeV DP Can have p-G3-X-G3-X-G3-p with M(X) ~ 12 GeV

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 20 QCD Google tev4lhc Fermilab Sept 2004 BNL Feb 2005 CERN Apr 2005 Fermilab Fall 2005

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 21 ATLAS Very small person (?) A “QCD machine”, especially if add forward detectors!

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 22

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 23 CMS at LHC Bigger people!

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 24 (MWPC TRACKING) CASTOR

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 25 Detecting Protons with x F > 0.9 K.Eggert’s talk

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 26 Central Exclusive Production gg fusion: main channel for H production. Another g-exchange can cancel color, even leave p intact. p p p + H + p Theoretical uncertainties in cross section, involving skewed gluon distributions, gluon k_T, gluon radiation, Sudakov ff etc. Probably ~ 0.2 fb at Tevatron, not detectable, but should be possible at LHC (higher L and ~ 3 fb?) at Tevatron 100 x Acc events in 30 pb^-1

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 27 Central Exclusive Higgs Production Can be inclusive (soft central hadrons) but exclusive (nothing else) is most interesting. Precision measurement of both p M(central) by MM Possible resolutions (~ 250 MeV at Tevatron) ~ 2 GeV at LHC. Can go for dominant H(110-130) b-bbar decay mode Exclusive DPE q-qbar dijets strongly suppressed (Jz = 0 rule) Selection Rule on central Q.Nos: Scalar... p correlations confirm (need statistics!) Non-SM H interesting!

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 28 Acceptances vs M x for p + p p + M x + p In addition to 215m (TOTEM) 420m detectors are essential for Mx < 400 GeV... region of H, WW, ZZ Both ATLAS & CMS want this. Join forces: FP420 project LOI for R&D LHCC June 05

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 29 FP420 = Forward Protons at 420 m Groups in ATLAS and CMS/TOTEM want to add very forward proton detectors, mainly to study “DPE”, central production. Central states especially : WW, ZZ, H, FP420 Valentina Avati Inelastic protons bent few mm out of beam 6mm x 24 mm detector (e.g. Si pixel) 25 mm 10 mm TOTEM

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 30 Albert De Roeck US

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 31 Diagrams for Prompt VV Pair Production in pp/ppbar Note different color flows in these diagrams can give different hadronic activity. (a)and (b) have color 3 annihilation (d) has color 8 annihilation (c) and (e) have color singlet exchange. (c) high pT q – forward jets; (e) low pT p’s – no jets, can be exclusive (Prompt i.e. not from top and not from Higgs)

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 32 Cross section for WW Production: Energy Dependence Tevatron cross section agrees with CTEQ NLO Tev2 sig(ZZ) = 1.39 pb sig (ZW) = 3.65 pb sig WW = 12.4 pb LHC ~ 10 x higher If Tevatron RoT apply, At LHC : SD, ~1% ~ 100 fb DP, ~ 10^-3 ~ 10 fb i.e. Guesstimate for DPE WW (ZZ) + anything ~ 10 (1) fb

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 33 Central Exclusive WW Production at LHC Nothing else on 2-lepton vertex! e + White Pomeron search

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 34 Double Pomeron W+W- via Q6 Loop Photon-Pomeron-Z vertex via Q6 loop Photoproduction at LHC? pp {p Z p} ~ 0 in SM

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Mike AlbrowRencontre de Blois May 2005QCD and Hard Diffraction at the LHC 35 Summary Tevatron is, and LHC will be, a cornucopia of QCD physics At LHC, Jets, W, Z, b, c, production, spectroscopy, decays and especially: rapidity gaps, exclusive production of jets, H, WW, ZZ, BSM Very Forward Proton Detection – New window on strong and electroweak interactions

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