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From HERA to LHC

From HERA to LHC. HERA – Tevatron – LHC: The decade of Hadron machines. Peter Schleper University of Hamburg. Strasbourg, March 12 th , 2004. HERA: Elektron-Proton E CMS = 320 GeV. LHC: Proton-Proton E CMS = 14 TeV. HERA – LHC:. QCD. Perturbative approach to QCD.

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From HERA to LHC

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  1. From HERA to LHC HERA – Tevatron – LHC: The decade of Hadron machines Peter Schleper University of Hamburg Strasbourg, March 12th , 2004

  2. HERA: Elektron-Proton ECMS = 320 GeV LHC: Proton-Proton ECMS = 14 TeV HERA – LHC: QCD

  3. Perturbative approach to QCD • QCD: SU(3) gauge theory • non abelian, self-interacting gluons, strong ! running coupling • extremely rich phenomenology • short distances: as small  perturbative calculations • factorisation of short (pert.) and long (non-pert.) scales • QCD predictions: • hard inter. • (N)NLO • Scale dependences: • as(Q2), f(x,Q2) A.Bhatti x = P(q,g) / P(p) momentum fraction x-dependence of f(x,Q2) not predicted Precision achievable / needed ?

  4. Benchmarks for Precision QCD The high energy frontier: Decade of Hadron colliders: HERA, Tevatron, LHC Higgs production at LHC Comparison NLO / NNLO • Discoveries depend on • input parton distributions • Extrapolation by QCD evol. • higher order calculations • non-pert. effects • for signal and background

  5. HERA Experiments: H1 & ZEUS Ee = 27.5 GeV Ep = 920 GeV • H1 & ZEUS: • Multi-purpose detectors • 2-3 layers silicon tracker • Drift chambers (~60 hits) • Forward: straw tubes • Hermetic calorimeters • (Uran-Sz. or Lar) • calibration ~ 1.5 % • B-field: 1.5 Tesla • Muon drift chambers • 100 Hz data taking • Trigger: 6 GeV for el.

  6. HERA 1 HERA 2 HERA II goals 500pb-1 e+ 500pb-1 e- e polarisation HERA I: 93-2000 100pb-1 e+ 15pb-1 e- • Strong focussing by • Magnets inside det. • Detector upgrades • Silicon tracking • Forward tracking • trigger 107 multi-hadronic events

  7. Background reduction • Focussing magnets ~1.5 m from vertex • Synchrotron radiation from e-beam • Direct synchr. largely shielded • Heating of beam pipe • bad dynamic vacuum • p-beam scatters on beam gas • high bkgr. • better shielding & vacuum system Accumulated Luminosity Expect: 135 pb-1 in 2004 ~ 1 fb-1 until 2007 Background problems solved: No limit on beam currents from experiments

  8. Kinematics at HERA and LHC HERA kinematics Neutral + Charged currents Q2 Q2 MZ Q2 LQCD Fixed target X X

  9. Quark densities - • Deep Inelastic Scattering • Neutral Current: • low Q2: q+q • high Q2: e-p – e+p ~ q-q • Charged Current: • e+p: u+c + (1-y2)(d+s) q+q - high sea,g - - - - Q2 - high sea quark density implies high gluon density Connection to Quark-Gluon Plasma: Colour Glass Condensate x

  10. High Q2 • g – Z interference • W exchange • e+ e- NC / CC NC low Q2: 1/Q4g propagator High Q2: M(Z,W) < Q propagators similar to g E-weak unification q-qbar x

  11. Charged Currents _ _ --- s (e-p) ~ x (u+c) + (1-y2) x (d+s) _ _ --- s (e+p) ~ x (u+c) + (1-y2) x(d+s) Charged currents HERA II Unfolding of parton distributions using CC and NC cross sections difficult to reach very large x>0.7 reduced cc cross section 2500 GeV2 700 GeV2 e+, 250pb-1 7000 GeV2 25000 GeV2 • e-, 250pb-1 x x

  12. Gluon density • HERA: Scaling violations, • FL ,charm • Tevatron: Jets Slope ~ as g(x,Q2) qq qg gg ET

  13. Parton Density fits • QCD fits to parton densities • Fit only inclusive DIS data: theoretically clean (H1,ZEUS,Alekhin) • Global fits: inclusive DIS, DY, Tevatron: jets, W/Z • more constraints (CTEQ,MRST,…) U Zeus/H1: fit to only HERA data ! similar precision as global fits uv g D dv Sea G

  14. Gluon Density: Charm at HERA depends in LO on gluon agrees with ZEUS NLO QCD fit

  15. Gluon Density: FL • NLO: contribution from gluons to FL H1 FL FL HERA III low EP run x x very sensitive: disfavors MRST

  16. Jets in g-p: HERA g-PDF & NLO describes data full HERA I luminosity Future: high x gluon ~ c.f.Tevatron

  17. as global as from QCD fits Bethke 2002 as from hadr. processses NNLO Very impressive success of QCD Limited everywhere by missing higher orders

  18. Higher Order Calculations • State of the art: • data unfolded with LO+PS monte carlo • results compared to NLO (+NLL) + hadr.cor.(LO+PS monte carlo) NNLO: building blocks known/calculated First results for DIS, Drell-Yan, Higgs,.. Within 1 ? year: 3 jets at LEP, 2-jet pp, 2-jet DIS the only way to precise as, sH Drell Yan at NNLO Monte Carlo: (the experimentalists view) Since ~5 years: 22,3,4 processes, LO+PS Needed: NLO + PS for unfolding data ! Better: NLO + NLL + PS the only way to precise data Both need strong support from the community !

  19. Higgs Production at LHC Benchmark test for status of QCD calculations Higher orders Parton densities uncertainty ~ 10 % uncertainty ~ 10 %

  20. Beauty & Charm Production • Beauty: Problem for QCD ? • Tevatron: data/theory ~3 … now much less • HERA: data/theory ~3 …. now … • LEP-gg: data/theory ~ 3 …. still high • Charm: • Tevatron slightly high • HERA and LEP-gg ~o.k. • 2 (3) scale problem: Mb, PTb, (Q2) • HERA/LEP-gg : Mb ~ PTb small, • Experimentally difficult: S/B ~ 1000 • B as part of gamma structure ?

  21. Beauty at HERA • Exp difficult: low PT jets, S/B ~ 1000 • Comparison data/theorie • Former: extrapolation of data to parton level and • full phase space with LO+PS monte carlo • Now: data as is, apply hadronisation corr. to NLO in visible phase space Deep inelastic Now agreement with NLO

  22. Beauty at HERA Photoproduction b b b Data still slightly above NLO, but main effect found: LO+PS differs from NLO invisible part of PS.

  23. Event Shapes at HERA • New: resummed calculations • fits to both means and shapes (H1) Dokshitzer-Webber ansatz: a0 = effective as below mI approx. for hadronisation NLO + PC NLO + NLL NLO + NLL + PC Jet Broadening

  24. Event Shapes at HERA Old result without resummation All event shapes well described by NLO + NLL + PC Fit to shapes Resummation + power correction very successful at HERA

  25. Parton Dynamics Selection: 2jets, unbalance DGLAP factorisation: integrated over trans. momentum f(x,Q2) expected to fail when Q~KT un-integrated PDFs: f(x,Q2,KT) BFKL,CCFM evolution NLO 3j NLO 2j Important at low –x High parton density

  26. HERA 2 HERA I 100pb-1 e+ 15pb-1 e- HERA II 500pb-1 e+ 500pb-1 e- expected 10 % error for Q2 > 16.000 GeV2 you can never have enough luminosity to beat 1/Q^4 and (1-x)^3 g-Z interference: e- constructive / e+ destructive

  27. helicity suppression e+ beampolarisation Feb 03 60 % Charged current Neutral current

  28. Conclusion • as: higher orders vital • Now: uncert. ~ 3 % • NNLO: 1-2 % possible Overall: QCD at HERA is in excellent shape • Beauty puzzle: • Much better agreement with theorie • Lack of good Monte Carlos • NLO Monte Carlo  LHC • Parton distributions: • pp H: uncert. 10 % • Requires new data from • Tevatron/DY/HERA Much progress in resummat., power corr., diffraction Ready for LHC ? not quite, but Tevatron RUN II, HERA II, THEORY…

  29. Benchmarks for Precision QCD as determinations: how good ? Zoom into SUSY Standard Model Supersymmetry Alpha_s figure Highest possible precision is vital !

  30. Power Corrections at LEP • Dokshitzer-Webber ansatz: • a0 = effective as below mI • approx. for hadronisation Fit to mean values Fit to shapes as = 0.1207 no consistent as shapes well described

  31. Charm at HERA

  32. Gluon Density: FL HERA II • simulation Longitudinal structure function H1 prel simulation of low Ep data [~ 460, 575, 920 GeV]

  33. Diffraction: factorization No colour exchange from Proton Soft QCD ? Hard scattering: Q2 large Factorisation in diffract. PDF and partonic s should follow DGLAP QCD evolution with Q2

  34. Diffraction in NLO QCD NLO QCD fits to incl data Same as in standard QCD fits to DIS PDF(x,Q2) for fixed Proton momentum Large gluon contribution Use diffr. PDF to predict s(jet) , s(charm)

  35. Diffraction in NLO QCD Jets Charm • NLO QCD fit to inclusive data describes jet and charm • successful test of hard scattering factorisation Current state: ~ all hard diffractive processes at HERA are described by NLO QCD

  36. Skewed partons • e.g.: DVCS (deeply virtual compton scattering) correlation between initial quarks and gluons f(x1,x2,Q2) Factorisation for large Q2 NLO successful

  37. event shapes & QCD resummed Inclusive jets: well described by NLO QCD

  38. Tevatron Jets CDF cone • Run I: 100 pb-1 • Run II: 200 pb-1 recorded • first prelim. results • CDF: 85 pb**-1, D0: 34 pb**-1 Run I gluon density not constrained at high x D0 KT Jet algorithms: Run I: cone, KT(D0) RUN II: also modified cone algor: midpoint algor.: additional seed allowed between found jets (P recomb. scheme, instead E) differences cone/ KT due to hadr. corrections

  39. Proton Structure many unknowns: uv, dv, us, ds, s, g many processes: DIS,Drell-Yan,Tevatron • Predictions depend on • QCD evolution • PDF’s at low Q2

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