1 / 40

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

ciro
Download Presentation

Ricerca del Bosone di Higgs a LHC

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related