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Ivo van Vulpen

Looking beyond the horizon using top quark physics at the LHC. Ivo van Vulpen. Layout talk. 1) Motivation: the SM and beyond. 2) Roadmap to discovery:  SM : Top quark physics at √ s = 14 TeV  Beyond : Anomalies in top quark events. VIDI proposal. 3) Workplan.

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Ivo van Vulpen

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  1. Looking beyond the horizon using top quark physics at the LHC Ivo van Vulpen

  2. Layout talk 1) Motivation: the SM and beyond 2) Roadmap to discovery:  SM: Top quark physics at √s =14 TeV Beyond: Anomalies in top quark events VIDI proposal 3) Workplan

  3. Limits on mh from theoryLimits on mh from exper. “We know everything about the Higgs boson except its mass” Higgs mass (GeV) Triviality Unitarity Λ (GeV) The Standard Model & the Higgs boson • The Standard Model: - Combines the EM, weak and strong force - Describes all measurements down to distances of 10-19 m • Electro-Weak Symmetry Breaking:(Higgs mechanism)- Weak gauge bosons and particles have mass- Regulate WW/ZZ scattering

  4. “All measurements in HEP can be explained using the SM” “The Higgs boson will be discovered at the LHC at ~ 150 GeV” NO ! Many open questions in SM. … but also things we do not understand: Gravity, Cold Dark Matter, Why 3 families, Why mt » me » mνHiggs:1) Higgs has not been discovered 2) Even if we do: hierarchy problem, or“Why is MEW « MPL ?”

  5. t W W t h h λtλt b Failure of radiative corr. in Higgs sector: Radiative corrections from top quark mh = 150 = 1354294336587235150–1354294336587235000 Λ2 The hierarchy problem Success of radiative corr. in the SM: predicted observed ? Hierarchy problem: ‘Conspiracy’ to get mh ~ MEW («MPL) Biggest troublemaker is the top quark!

  6. (MPL is a few TeV) (several new particles) (boson loops cancel fermion loops) Solutions to the hierarchy problem Extra Dimensions Little Higgs Higgsless SUSY Standard Model ? mSUGRA GMSB AMSB

  7. SM Anomalies model 4 Take a topology that is:- a well calculable SM candle - sensitive to several hypotheses simultaneously tt Most models predict signature visible in top quark pair production Main idea / approach Idea 1: Do not concentrate on a specific model (model 1,2, …) Look for fingerprint of new physics in specific topology SM model 1 model 2 model 3 Data model 4 model 5 model 6

  8. The ATLAS detector at the LHC Process #events #events sec-1 10 fb-1 The LHC collider: T - 500 days … Luminosity per year:2007: 100 pb-1Nominal: 10 fb-1 The ATLAS detector: First year:Enormous reach for new physics. Need to understand detector and SM at √s =14 TeV.

  9. Top physics at the LHC • Top production at the LHC: 85 % 7.5 million events/year NLO Monte Carlo 2) Measure top properties:Charge, couplings, mass, cross section, …. 3) Use tt events as a calibration tool: Complex topology with multiple constraints

  10. 4/9 2) A candle for complex topologies: Calibrate light jet energy scale Calibrate missing ET Obtain enriched b-jet sample Leptons & Trigger Top physics at the LHC “Top quark pair production has it all”: ≥4 jets, b-jets, neutrino, lepton several mass constraints for calibration Note the 4 candles: - 2 W-bosons Mw = 80.4 GeV- 2 top quarks & Mt = Mt-bar

  11. LHC day 1: See the top • Standard-analysis: 2 b-jets  S/B ~ 80 • Commissioning-analysis: no b-tag (robust cuts) Hadronic 3-jet mass ATLAS Events / 4.15 GeV L=100 pb-1 mtop Mjjj (GeV)

  12. Z’, ZH, G(1),SUSY, ? Gaemers, Hoogeveen (1984) 500 GeV 600 GeV 400 GeV LHC day 2: Resonances ? Structure in Mtt Resonances in Mtt Interference from MSSM HiggsesH,A tt (6-7% effect) Resonance of 1600 GeV Δσ/σ ~ 6 % # events Cross section (a.u.) Mtt (GeV) Mtt (GeV)

  13. Sensitive to hard scale: jet jet jet ATLAS 10 fb-1 (1 year) SUSY Discovery jet/lepton # events/400 GeV jet/lepton Meff (GeV) tt production dominant backgroundremember: we understand this  After 1 year reach ~ 2 TeV for MSUSY LHC day 2: First to discover SUSY In R-parity conserving models the LSP is stable and escapes detection (mSUGRA) Topology: ≥4 jets missing ET (large) leptons/photons SUSY events are in top sample!

  14. Plan of research Commissioning analysis: 4 jets+lepton +missing ET InvestigateHadronic-side Investigate leptonic side Improve lepton identif. and trigger in multi-jet events Calibrate missing ET Reconstruct total tt-system. Measure differential cross section. Calibrate Jet energy scale Select clean b-jet sample Develop constrainedfittingpackage Extra leptons in tt-like events … SUSY Resonances in

  15. 2007 2006 2008 2009 2005 Plan of work 2010 2011 Rediscover the topconfidence! 1) Prepare for first data: - Calibration strategy & trigger - Constrained fitting - Weltmeister! 2) SM Top physics:- Cross section (leptons) - Jet energy scale 3) Beyond the SM:- Structure in Mtt - SUSY with leptons - ? BONUS Possibility to divert interest quickly if anomaly appears in unexpected topology

  16. Summary Base scenario: Top physics: Important scientific program! Great scenario: Hint of new physics elsewhere: extra information from top sector Perfect scenario: New physics strong in top sector  discovery!

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