PHANTOM Update
Ezio Maina
U. of Torino
Physics at TeV Colliders Workshop - Les Houches 2007
Phantom
Ballestrero, Belhouari,Bevilacqua,E.M.
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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
qqVV prod
VV scattering
Higgs
top
VV couplings
Exact vs VVqq-Prod⊗Decay
uu→uuqqμν
qq=u-dbar,c-sbar
Single process
mh=500GeV
MADEVENT: qqWV⊗Decay
Could produce exact result
Tuned comparison
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?
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
NOT UNIQUE!!
Works well in ππ
Small s ⇒ LET
Large s ⇒ aj→1
Models of EWSB 2
Additional dynamics,dimensions …….
Model Independent Low Energy parametrization of composite Higgs models
Giudice,Grojean,Pomarol,Rattazzi hep-ph/0703164
Barbieri,Bellazzini,Rychkov,Varagnolo arXiv:0706.0432
 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
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
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
Looking for Mr. V Boson
Butterworth, Ellis, Raklev hep-ph/0702150
W jets
Jet in
W+jet
70<M<90 GeV
pT > 250 GeV
Alternatives?
qq→4qlv O(α6)+O(α4αs2)
Ballestrero, Bevilacqua,E.M.
WVjj ✔
Wjjjj ✘
Closer to the real world
Preliminary
CMS Note 2007/005
Torino+ Milano CMS Group+TH
430 fb-1 needed for S/B1/2=5 in 4qev
FAMOS
Bkg:Alpgen+Madevent
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
Backup slides
Boson-Boson scattering and Unitarity
Selection 4qμν
CMS Note
Selection 4qeν
CMS Note
Selection 4qeν continued
Efficiency