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Ricerca del Bosone di Higgs a LHC

Ricerca del Bosone di Higgs a LHC. Landau Pole : la costante di accoppiamento diventa infinita. Higgs Width vs M Higgs. Per alte masse diventa indefinito. I diagrammi con H cancellano la crescita quadratica del primo diagramma

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Ricerca del Bosone di Higgs a LHC

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  1. Ricerca del Bosonedi Higgs a LHC

  2. Landau Pole: la costantediaccoppiamentodiventainfinita

  3. Higgs Width vsMHiggs Per alte masse diventaindefinito

  4. I diagrammi con H cancellano la crescitaquadratica del primo diagramma Se non esistel’Higgs, deveesisterequalcosadianalogo !!!

  5. Ricerca del Bosonedi Higgs al LEP e+ X Zo X Zo * Ho b e- B-tag b Ecmmax = 207 GeV MHmax ~ Ecmmax - Mzo~ 116 GeV

  6. Poisson Statistics: probability of obtaining k events if λ events are expected on average (the mean): P(k,λ) = e-λ·λk k!

  7. Probabilita’ diosservare n candidati, ognuno con xjdiunacertavariabilediscriminante (es. Massa, lunghezzadidecadimento, etc, nell’ipotesisegnale + fondo ): Pj= probab. cheilcandidato j abbiailvalorexj Dove S(xj) e B(xj) sono la probab. chexjsiasegnale o fondo. e’ ilnumerodieventidisegnale con valorexj, etc… wj e’ un peso a secondachel’eventosiapiu’ signal-like o background-like

  8. Genero Q nell’ipotesidi solo fondo. Genero Q nell’ipotesisegnale + fondo Li confronto con Q osservato (un valore) dove s e’ calcolatonell’ipotesi di solo fondo Idea di base: verificare se Idati osservatisonopiu’ compatibili con unaipotesidi solo fondo, o disegnalepiu’ fondo observed

  9. observed

  10. Q = Ls+b/Lb Likelihood conipotesidisegnale + background Likelihood con ipotesidi solo segnale http://lephiggs.web.cern.ch/LEPHIGGS/papers/LEP-SM-HIGGS-PAPER/index.html (cisiarrivadaLep Electroweak Working Group webpage)

  11. Il “segnale” vistodal LEP

  12. Pesideglieventi “Higgs-like”

  13. Un modoalternativodimostrarei plot diesclusione • Limitesuperioreallasezioned’urto per produzionedi Higgs, Rlim • (Se non ho abbastanzasensibilita’, posso dire che • σobs(Higgs, 95 CL) < X, al 95 % CL.) • Confronto con σ(Higgs SM), ovvero X = σ(Higgs SM). • Rlim = σ(Higgs, 95 CL)/σ(Higgs SM) vs MH • Se Rlim < 1 siesclude la produzionedi Higgs, rispetto al Modello Standard Limiteattuale del Tevatron

  14. Tevatron per MH < 150 GeV And below 115 GeV ?!?!?!

  15. LLR = Ls+b/Lb

  16. X-sec ~ 1 fb 100 event = 100 fb-1

  17. Parton Distribution Functions nelprotone LHC e’ unamacchinadigluoni

  18. La produzionedagluoni e’ dominante a LHC Branching Ratio didecadimento Sez. d’urtodiproduzione (fb)

  19. Accoppiamentidell’Higgs: gHVV ~ m2V (1/sin 2Ɵw per le W) gHff ~ mf

  20. H→gg Raro ma in lineadi principio facile daidentificare t g H g t Branching Ratio didecadimento

  21. Mass measurement at the level of 100-200 MeVis possible with enough luminosity 30 fb-1

  22. N.B. Nel run appenainiziato e’ previsto 1 fb-1 (a 7 TeV)

  23. ttH, H→bb Grande sezioned’urto, ma fondialtissimi. Riservatoaimaniaci, e solo se l’higgs e’ gia’ statoscoperto Branching Ratio didecadimento

  24. CMS, ttH, H→bb, 60fb-1 • ttH in CMS : Working point 60fb-1 • Studies three final states: • fully hadronic :ttH -> bbbbqqqq • fully leptonic :ttH -> bbbblnulnu • Semi-leptonic:ttH -> bbbbqqlnu (l=e or mu)

  25. qqH , H→tt Un ragionevolecompromesso frasez. d’urto e fondo Branching Ratio didecadimento

  26. In CMS with early data of 1fb-1 only an upper limit on the cross section can be established. (Worse at 7 TeV)

  27. H→W W Canalemigliore per MH ~ 2 Mw W H W* Branching Ratio didecadimento

  28. 1)Cut-based analysis: W lν, l = e, µ • Kinematic distributions of signal and background events: • A low lepton pair Δφ and invariant mass is expected for the signal events compared to backgrounds, • After all selection cuts there are 31 events of emu signal and 31 background at 1fb-1 Masses lower or higher than m(H)=160GeV leave less signal and more background.

  29. 2) Multivariate analysis: The neural net analysis gives better results than cut based analysis: At 1 fb-1with m(H)=160GeV, Cut based analysis : S/B=70/70, NN analysis : S/B=67/37 Best range

  30. H→ZZ Canalepiu’ pulito per alte masse Z H Z* Branching Ratio didecadimento

  31. Higgs boson candidate mass at preselectionlevel (@ 1 fb-1) Selection cuts

  32. Ricostruzionemassa Z e Z* H→ZZ, 1fb-1 @14 TeV !!! Ricostruzionemassa H

  33. Quasi escluso !

  34. Previsioni a 1 fb-1 1 fb-1 esclusione 145-190 GeV M. Diemoz

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