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Higgs, Top and Boson Boson Scattering Six fermion simulations at the LHC

Higgs, Top and Boson Boson Scattering Six fermion simulations at the LHC . E. Maina U. Torino. MCWG Frascati Feb 27, 2006. LHC Physics Agenda. Higgs (SM?) SUSY No Higgs nor SUSY Top QCD …………. SM Higgs discovery. H→μeνν. Asai et al. What if no Higgs?. Consistency of SM is lost

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Higgs, Top and Boson Boson Scattering Six fermion simulations at the LHC

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  1. Higgs, Top and Boson Boson Scattering Six fermion simulations at the LHC E. Maina U. Torino MCWG Frascati Feb 27, 2006

  2. LHC Physics Agenda • Higgs (SM?) • SUSY • No Higgs nor SUSY • Top • QCD • …………

  3. SM Higgs discovery H→μeνν Asai et al.

  4. What if no Higgs? • Consistency of SM is lost • SM Effective theory • Why does SM with weak radiative corrections work so well? • MSSM not a viable replacement EWWG 05 Where do we look for clues to what lies beyond SM ?

  5. Boson-Boson scattering and Unitarity

  6. Unitarity • Expand Amp in partial waves M=∑j aj (s) Pj(cos(ϑ)) • SS†=1 ⇒ |aj(s)|≤1 • Low Energy Th. M(VV→VV)∝s/v2 No H Unitarization: one example aj = a0j /(1-ia0j) a0j∝s Small s ⇒ LET Large s ⇒ aj→1 NOT UNIQUE!! Works well in ππ

  7. Unitarization: eg: Butterworth,Cox,Forshaw PRD65(02)96014different ways of constructing amplitudes which are unitary from low order amp Must be prepared for the unexpected Must know SM “background” e.g VTVT

  8. t-tbar, qqH, VV→VV requireMultiparton ME MC’s • Dedicated: ALPGEN, GR@PPA …. • General purpose, automatic: MADEVENT, COMPHEP, GRACE, AMEGIC …. • NLO: MC@NLO match NLO calculation with PS No full EW six fermion MC : enter PHASE, PHANTOM QCD is flavour blind: smaller number of basic amps

  9. PhantomBallestrero, Belhouari,Bevilacqua,E.M. • Dedicated event generator O(α6)+O(α4αs2) • All q1q2→f1f2 f3 f4 f5f6, gg →f1f2 f3 f4 f5f6 , gq→…… • Exact matrix elements. No production ⊗decay or EVBA • One-shot: generates unweighted events for all processes simultaneously • Efficient: good coverage of phase-space • Interfaced with showering/hadronization via LH protocol • Interfaced with FAMOS (as Phase1.0) • Overcomes Problems due to • Large number of processes • Large number of diagrams/process • Large number of channels/enhanced regions q1q2→q1q2 q3 q4 lv covered in Phase1.0 Accomando,Ballestrero,E.M. hep-ph/0504009

  10. Phantom 0.9 : qq→4qlv At O(α6) All particles outgoing Adding ud↔cs, e ↔μ, CC ⇒1K processes All processes generated simultaneously Two step procedure As in Phase 1.0

  11. Phantom 0.9: qq→4ql⁺l⁻ O(α6) Good generation efficiency ≈ 10-3

  12. PHACT PLB350(95)225hep-ph/9911318

  13. I=〈f〉A ΔI∝〈(f−〈f〉)2 〉

  14. Adaptive integration (VEGAS) • Adapts well to cuts • Rough estimate of integrand shape usually enough • Fails if too many peaks or along diagonals • Multichannel • Requires a large number of channels • All channels are integrated over simultaneously • Sensitive to cuts, efficiency generally small • Adapts varying the channel relative weight • Iterative-Adaptive Multichannel NEW! (Phase+Phantom) Merges best feautures of both! • Adapts well to cuts • Rough estimate of integrand shape enough • Small number of channels required (Multimapping) • Channels are integrated separately • Good efficiency

  15. An interesting example: 1046 diagrams It includes: • ZZ → W+W- Higgs → WW • ZW- → ZW- • W-Z → ZW- • W-W- → W-W- • W- → W-W+W- 2 Higgs → WW chanls • W- → ZZW- Higgs → ZZ Homework: check it out

  16. First results qq→4qlv Accomando,Ballestrero,Bolognesi,E.M.,Mariotti hep-ph/0512219

  17. Selection Tag vs decay quarks

  18. Signal vs Bkg Bad

  19. After: Top rejection W mass PHASE vs PYTHIA mH=500 GeV No Higgs PYTHIA has only LL in EVBA approximation

  20. PHASE vs MADEVENT uu→uuqqμν Not the full set of processes qq=u-dbar,c-sbar MADEVENT: qqWV⊗Decay Could produce exact result Long CPU time VVV production vetoed

  21. M(VW)>800GeV +pT+E+η+Mij cuts Small sensitivity to MH in SM range ⇒ SM predictions well defined. Not just counting exp

  22. qq→qqH, H→ZZ, ZZ→llqq Accomando, Ballestrero, Belhouari, E.M. in preparation EW bkg + interference included exactly bkg ≈ 10% exact spin correlations

  23. M(VZ)>800GeV +pT+E+η+Mij cuts ηqc Red lines: |ηZ| < 2 |ηqc| < 2 Full: noH Dash:mh=200 GeV

  24. Internal gluon QCD correctionswith G. Bevilacqua (Torino) Includes qq→tt No external g All qq→4qlv processes 70<M(jcjc)<90GeV First results: no real analysis

  25. Improvements and projectsPhantom 1.0qq→6f O(α6) as first step • 2q → 2q4l ready WW&ZW&ZZ final states lept • 2q → 4qlnu @ O(αs2 αw4) first results available • 2g → 4qlnu @ O(αs2 αw4) ready Main TOP channel! Good control of tails is essential • 2g → 4ql⁺l⁻ ready • 2g → 2q4l ready • 2q → 4ql⁺l ⁻@ O(αs2 αw4) • t-tbar: spin correlations • qqWW→qqlνlν • Alternative models of EWSB • Standard candle

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