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(The Uncertainties Of)

(The Uncertainties Of). Higgs Discovery at the LHC. OR Hunting the (non-SUPAsymmetric) Higgs. Tony Doyle. OR The Iceman Cometh. Outline. Ingredients Motivation Constraints Dependencies Collider Detector Grid Analysis. Discovery? When?. Introduction.

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(The Uncertainties Of)

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  1. (The Uncertainties Of) Higgs Discovery at the LHC ORHunting the (non-SUPAsymmetric) Higgs Tony Doyle ORThe Iceman Cometh Particle Physics Theme Launch

  2. Outline • Ingredients • Motivation • Constraints • Dependencies • Collider • Detector • Grid • Analysis Discovery? When? Particle Physics Theme Launch

  3. Introduction • The Iceman Cometh? exposes the human need for illusion as an antidote to despair.. • The Iceman Cometh exposes the physicist need for a goal as an antidote to building a machine/detector/computer system/simulation * *delete as applicable • Apologies to Eugene O’Neill • Thanks to Peter Higgs.. Particle Physics Theme Launch

  4. Where Theory meets Experiment Particle Physics Theme Launch

  5. The Higgs Mechanism Higgs potential: V()= -2+ + (+)2 (>0) =exp(ia(x)T’’a) |0 . (0 + H(x)) mH = 2 (a free parameter) Theory: vacuum potential The ultimate green field site Energy Ready to interact Particle Physics Theme Launch

  6. LHC Motivation: Higgs Production in pp Collisions q Z0 q1 W W H q2 p p Z0 q unitarity arguments mH ≤ 1 TeV (Lee et al, 1977) MH ≤ 1000 GeV EW ≥ 500 GeV E1 ≥ 1000 GeV E2 >≥ 1000 GeV Parton luminosities Ecm=(4x1x2.EpEp)  Proton Proton Collider with Ep ≥ 7 TeV Particle Physics Theme Launch

  7. LHC Motivation: Higgs Discovery Potential For 30 fb-1, the Standard Model Higgs can be discovered over the full allowed mass range  End of talk? Particle Physics Theme Launch

  8. logarithmic sensitivity to mH: • Measured mt=172.7  2.9 GeV 3 GeVshift in measured mt causes ~20% shift in mH • Preferred mH = 91 GeV • Incl. theory uncertainty gives mH < 186 GeV (95% CL) • Does not incl. LEP2 direct search limit: mH > 114.4 GeV (95% CL) • Renormalise probability (mH >114.4 GeV) to 100%, then mH <219 GeV (95% CL) Latest Electroweak Fits Greater focus on the light Higgs Particle Physics Theme Launch

  9. Tevatron direct search • Tevatron may be able to exclude a light Higgs (mH<130 GeV) • Given sufficient luminosity, evidence for a light Higgs still possible L [fb-1 ] Combined CDF and D0 Updated in 2003 in the low Higgs mass region W(Z)Hln(nn,ll)bb to include 1. better detector understanding 2. optimised analysis 10 fb-1/expt 4 fb-1/expt Particle Physics Theme Launch

  10. A. When cometh the LHC? Particle Physics Theme Launch

  11. A. When cometh the LHC? • Stages: • • Establish injection conditions • • Fill • • Ramp up • • Squeeze • • Prepare physics • • Physics • • Standard beam dump • Non-trivial 7+7 = 14 TeV Ultimate design luminosity (SUPA-LHC?) L = 1034 cm-2s-1 = 10 events nb-1 s-1 or 100 events fb-1 yr-1(continuous running) Realistically expect? Particle Physics Theme Launch

  12. LHC Startup Planning “Main objectives are to terminate installation in February 2007 and enable first collisions in summer 2007” Lyn Evans Particle Physics Theme Launch

  13. LHC Commissioning(in 4 stages) Stage 1: Initial commissioning to pilot physics Stage 2: 75 ns (Nominal emittance, full crossing angle) Stage 3: 25 ns (Limited intensity) Stage 4: 25 ns (Performance) Particle Physics Theme Launch

  14. A. When cometh the LHC? • Stages: • • Establish injection conditions • • Fill • • Ramp up • • Squeeze • • Prepare physics • • Physics • • Standard beam dump • Non-trivial 7+7 = 14 TeV Ultimate design luminosity (SUPA-LHC?) L = 1034 cm-2s-1 = 10 events nb-1 s-1 or 100 events fb-1 yr-1(continuous running) Realistically expect? 2007 2008 2009 collisions ~2fb-1 ~10fb-1 Particle Physics Theme Launch

  15. Bat 40 B. When cometh ATLAS? not where.. the detector will end up Particle Physics Theme Launch

  16. The ATLAS Detector ATLAS = large international collaborationto find the Higgs (and much more) in the range 0.1TeV < mH < 1TeV The ATLAS experiment is 26m long, stands 20m high and weighs 7000 tons SCT alone has 6.2 million read-out channels Particle Physics Theme Launch

  17. ATLAS Status Significant Progress All four completed SCT barrel cylinders have been integrated in their thermal enclosure The barrel LAr and Tile calorimeters are in their ‘garage position’. LAr end-cap C on its way A cosmic muon registered in the barrel Tile calorimeter Integrated end-cap TRT wheels Particle Physics Theme Launch

  18. B. When Cometh ATLAS? “with good will and great efforts from everybody we can be confident that the Technical Coordination Team will manage to have ATLAS installed by June 2007” Particle Physics Theme Launch

  19. C. When Cometh the Grid? • Aim: by 2008 (full year’s data taking) • CPU ~100MSi2k (100,000 CPUs) • Storage ~80PB • - Involving >100 institutes worldwide • Build on complex middleware being developed in advanced Grid technology projects, both in Europe (Glite) and in the USA (VDT) • Prototype went live in September 2003 in 12 countries • Extensively tested by the LHC experiments in September 2004 • Currently 197 sites, 13,797 CPUs, 5PB storage in September 2005 Particle Physics Theme Launch

  20. What is the LHC Computing Challenge? a. Rare Phenomena Huge Background b. Complexity All interactions 9 orders of magnitude The Higgs • “one in a billion events” • “millions of readout channels” Particle Physics Theme Launch

  21. Meeting Analysis Requirements… • Requirements = Pledges • Compare • (a) Bottom up • (b) Top down √ Particle Physics Theme Launch

  22. C. When Cometh the Grid? • Service Challenges – UK deployment plans • End point April ’07 • Context: the virtual LHC Computing Centre Particle Physics Theme Launch

  23. Production ModesEcm=(4x1x2.E1E2) Vector Boson Fusion ggH Associated Hbb (large backgrounds) HZ (low significance) Particle Physics Theme Launch

  24. ▬ ▬ √ √ √ ~ √ √ √ √ √ √ ~ ~ ~ bb   ~ ~ √ WW ZZ Decay Modes large irreducible backgrounds for tt, cc and gg decay modes, Zg Particle Physics Theme Launch

  25. Light Higgs • Various decay modes: • mH<130 GeV: tt Hl X bb • mH<150 GeV: H • mH<150 GeV: Htt • 130< mH<2 mZ:HWW(*)l l • 130< mH<700 GeV:HZZ(*)l l l l • 700< mH<1 TeV:HZZll HWWl jj • “(no K-factors)” = conservative [ATLAS 04] 5 Particle Physics Theme Launch

  26. Higgs Production Corrections and Uncertainties PDF Comparison: CTEQ6, MRST2002, Alekhin • example: σ(mH=120 GeV) @ LHC The HO pQCD corrections to (gg→H) are large (more diagrams, more colour) can improve NNLO precision slightly by resumming additional soft/collinear higher-order logarithms Particle Physics Theme Launch

  27. g H t g g H g Higgs Production Corrections and Uncertainties Djouadi & Ferrag, hep-ph/0310209 *Increase of cross section compared to lower order (correction - not an uncertainty) Not just LO, NLO, NNLO… also resummations threshold logs logN(1-M2/sgg)  σtheory  ± 9% Catani et al, hep-ph/0306211 Particle Physics Theme Launch

  28. ATLAS 30 fb-1 Analysis Methods e.g. Hbb, via ttH • Complex decay channel: • One lepton (trigger) • 4 b-jets + 2 jets  Need excellent b-tagging • Fully reconstructed t • High jet multiplicity  combinatorials • Background: • Reducible: tt+jj, W+jets • Extracted from data • Irreducible: ttbb, combinatorials • Discovery potential with 30 fb-1: MH < 125 GeV Particle Physics Theme Launch

  29. NLO Background Example ATLAS 30 fb-1 t b t b the more external coloured particles, the more difficult the NLO pQCD calculation Example: pp →ttbb + X bkgd. to ttH the more particles, the more difficult the whole analysis the leading order O(αS4) cross section has a large renormalisation scale dependence Particle Physics Theme Launch

  30. Analysis Methods e.g. H  gg 1. Radiation lengths 3. NLO corrections 2. Primary vertex 4. inc. recoil jet (all/unconverted/converted g’s) An “easy” decay mode (30 fb-1) “easy” is relative Particle Physics Theme Launch

  31. Two or more channels in complete light mass range • Enhance early Higgs discovery? • ATL-PHYS-2004-034 (2004) Combined Analysis • Requires an understanding of (all of) the individual signals, backgrounds and the relative systematic uncertainties… The Icemen Cometh 2009 2008 • Invert the problem • “Luminosity required for discovery?” • Assume the LHC luminosity guesstimates are correct… Particle Physics Theme Launch

  32. A (Light) Summary Priors indicate a Higgs mass 114.4 < mH [GeV] <219 A Grid service will be launched in April 2007 The ATLAS detector will be complete in June 2007 The LHC will provide first collisions in Summer 2007 These will enable data analyses such that the Higgs will be discovered on May 29th 2009 probably… large corrections “Of course I like it when they give seminars on the search for the Higgs and so on…” Particle Physics Theme Launch

  33. How the Higgs will feel on his 80th birthday? what have I done? Of course I like it when they give seminars on the search for the Higgs and so on. And of course I think it's important to look for. But you want to know the truth, when I consider the huge sums going for this, the lifetimes spent on the search, I can't help but think: “Good heavens, what have I done?” Peter Higgs The last Barrel Toroid coil was moved into position on 25th August and the structure was released from the external supports on 29th September Particle Physics Theme Launch

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