PHANTOM 1 0 Higgs Top and Boson Scattering

PHANTOM 1. 0 Higgs, Top and Boson Scattering Six fermion simulations at the LHC E. Maina U. Torino MC 4 LHC July 17, 2006 1

Phantom Ballestrero, Belhouari, Bevilacqua, E. M. § § § § Dedicated event generator Complete 2→ 6 O(α 6)+O(α 4αs 2) q 1 q 2→f 1 f 2 f 3 f 4 f 5 f 6 O(α 6)+O(α 4αs 2) gg → f 1 f 2 f 3 f 4 f 5 f 6, gq→gq f 1 f 2 f 3 f 4, qq→gg f 1 f 2 f 3 f 4, Exact matrix elements. No production⊗decay or EVBA Fast One-shot: generates unweighted events for all processes simultaneously Efficient: good mapping of phase-space q 1 q 2→q 1 q 2 q 3 q 4 lv covered in Phase 1. 0 Accomando, Ballestrero, E. M. hep-ph/0504009 2

VV scattering Higgs top VV couplings 3

An interesting example: 1046 diagrams It includes: • ZZ → W+WHiggs → WW • ZW- → ZW • W-Z → ZW • W-W- → W-W • W→ W-W+W- 2 Higgs → WW channels • W→ ZZWHiggs → ZZ 4

n Adaptive integration (VEGAS) ü ü ü n Multichannel ü ü n Adapts well to cuts Rough estimate of integrand shape usually enough Fails if too many peaks or along diagonals 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! ü ü ü Adapts well to cuts Rough estimate of integrand shape enough Small number of channels required (Multimapping) Channels are integrated separately Good efficiency Two steps: • Grid generation • Event generation: one shot 5

qq→ 4 qlv PHASE vs PYTHIA m. H=500 Ge. V After: Top veto, W mass cut p. TW >50 Ge. V in WW CM No Higgs PYTHIA has only LL in EVBA approximation 6

PHASE vs MADEVENT uu→uuqqμν qq=u-dbar, c-sbar Single process MADEVENT: qq. WV⊗Decay Could produce exact result Long CPU time Tuned comparison VVV production vetoed 7

qq→ 4 qlv(EW) M(VW)>800 Ge. V +p. T+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 8

Internal gluon QCD corrections with G. Bevilacqua (Torino) Includes qq→tt No external g All qq→ 4 qlv processes First results: no real analysis 70<M(jcjc)<90 Ge. V 9

Phantom 1. 0 § Fast, efficient, dedicated event generator § Complete 2→ 6 O(α 6)+O(α 4αs 2) § Exact, complete LO ME Projects: t-tbar: spin correlations n qq. WW→qqlνlν n Alternative models of EWSB n 10

qq→ 4 qlv All particles outgoing Adding ud↔cs, e ↔μ, CC ⇒ 1 K processes 16 amplitudes 2 basic sets of diags Total: 5 basic sets 4 W, 2 Z 2 W, 4 Z 2 g. Z 2 W, 2 g 3 Z 11

Accomando, Ballestrero, Bolognesi, E. M. , Mariotti hep-ph/0512219 First results qq→ 4 qlv 12

PHACT PLB 350(95)225 hep-ph/9911318 13