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Advances in Event Generation for Higgs and Weak Boson Scattering at TeV Colliders

This workshop report details the PHANTOM event generator, focusing on its capabilities related to weak boson scattering and Higgs interactions. It presents a comprehensive approach to simulating complex 2→6 processes up to O(α6) and O(α4αs2), including various interactions like pp and e+e-. We discuss exact matrix elements without production-decay or EVBA approximations, emphasizing the efficiency and accuracy of the generator in phase space mapping and multichannel events. The significance of studying electroweak symmetry breaking (EWSB) and associated resonance dynamics in this context is highlighted.

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Advances in Event Generation for Higgs and Weak Boson Scattering at TeV Colliders

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  1. PHANTOM Update Ezio Maina U. of Torino Physics at TeV Colliders Workshop - Les Houches 2007

  2. PhantomBallestrero, Belhouari,Bevilacqua,E.M. • Dedicated event generator • Complete 2→6 O(α6)+O(α4αs2) • p-p, p-pbar, e+e-- • Complete set of reactions up to pp→ 4l2j, ee → 2l4j • At LHC: q1q2→f1f2 f3 f4 f5f6 O(α6)+O(α4αs2) gg → f1f2 f3 f4 f5f6, gq→gq f1f2 f3 f4, qq→gg f1f2 f3 f4 • Exact matrix elements. No production⊗decay or EVBA • Fast • One-shot: generates unweighted events for all processes simultaneously • Efficient: good mapping of phase-space • Multichannel + Vegas q1q2→q1q2 q3 q4 lv covered in Phase1.0 Accomando,Ballestrero,E.M. hep-ph/0504009

  3. qqVV prod VV scattering Higgs top VV couplings

  4. Exact vs VVqq-Prod⊗Decay uu→uuqqμν Single process qq=u-dbar,c-sbar mh=500GeV MADEVENT: qqWV⊗Decay Could produce exact result Tuned comparison

  5. VV scattering with PHANTOM • Light Higgs ➙ VV weakly coupled Higgs Found ➙ check VV scattering Are SM predictions verified? • Heavy (No) Higgs ➙ VV strongly coupled Higgs Not Found ➙ check VV scattering What restores Unitarity?

  6. Models of EWSB Electroweak Chiral Lagrangian Butterworth,Cox,Forshaw PRD65(02)96014 Fabbrichesi,Vecchi hep-ph/0703236 many others • Expand LL → LL 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. Models of EWSB 2 Additional dynamics,dimensions ……. • Higgs low energy “remnant” of High Energy Strong Dynamics • Severely constrained by EW Precision Tests • Additional states may appear as resonances (Model dependent) • Reduced HVV couplings ➙ Partial restoration of Unitarity up to the High Energy scale Model Independent Low Energy parametrization of composite Higgs models Giudice,Grojean,Pomarol,Rattazzi hep-ph/0703164 Barbieri,Bellazzini,Rychkov,Varagnolo arXiv:0706.0432

  8. qq→4qlv(EW) M(VW)>800GeV +pT+E+η+Mij cuts Small sensitivity to MH in SM range ⇒ SM predictions well defined. Not just counting exp Accomando,Ballestrero,Bolognesi,E.M.,Mariotti JHEP 0603(2006)093 hep-ph/0512219

  9. qq→4qμ+μ--(EW) M(VZ)>800GeV +pT+E+η+Mij cuts Accomando,Ballestrero,Belhouari,Maina PRD 75:113006,2007 hep-ph/0603167 100 fb-1 |ηV|< 2

  10. Looking for Mr. V Boson Butterworth, Ellis, Raklev hep-ph/0702150 Jet in W+jet W jets 70<M<90 GeV pT > 250 GeV Alternatives?

  11. qq→4qlvO(α6)+O(α4αs2) Ballestrero, Bevilacqua,E.M. WVjj ✔ Wjjjj ✘

  12. Closer to the real world FAMOS CMS Note 2007/005 Preliminary Torino+ Milano CMS Group+TH Bkg:Alpgen+Madevent 430 fb-1 needed for S/B1/2=5 in 4qev

  13. Conclusions • Studying EWSB through VV scattering is hard • Semileptonic channels essential • New techniques for reconstructing hadronic V’s needed Plans • Complete qq→4qlv • Alternative models of EWSB

  14. Backup slides

  15. Boson-Boson scattering and Unitarity

  16. Selection 4qμν CMS Note

  17. Selection 4qeν CMS Note

  18. Selection 4qeν continued

  19. Efficiency

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