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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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