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Searching for Higgs Bosons at LHC (CMS emphasis)

This article discusses the search for Higgs bosons, with a focus on the CMS experiment at LHC. It covers new analysis developments and discovery potential, as well as background data and advanced generators for multi-jet events. The article also provides information on SM and MSSM Higgs bosons, including Higgs couplings and production cross sections.

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Searching for Higgs Bosons at LHC (CMS emphasis)

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  1. Searches for the Higgs boson(s) at LHC (emphasize on CMS)A. Nikitenko, IC, London. On leave from ITEP, Moscow CERN, Building 40 ATLAS CMS LHC Days in Split, 2-8 October 2006

  2. New Analysis Developments from CMS http://cmsdoc.cern.ch/cms/cpt/tdr/ • CERN/LHCC 2006-001 CERN/LHCC 2006-021 • Published submitted to LHCC

  3. CMS PTDR vol.2 was submitted to LHCC in 20th of June (2006) • Discovery potential for the Higgs boson(s) was updated in comparison with Higgs Summary CMS Note 2003/033 : • Latest trigger table • Background from “data”, exp. systematics • Advanced generators for multi-jet events: ALPGEN, MadGraph, CompHEP, TopRex • almost all analyses use full G4 simulation data • L = 2 x 1033cm-2s-1

  4. Cont. • NLO cross sections was used for Higgs boson production and backgrounds (when available) • SM Higgs boson: HDECAY, HIGLU, VV2H, V2HV, HQQ. Summary Tables provided by M. Spira. Table withPDF uncertainties of s (H) provided by A. Djouadi • MSSM Higgs bosons: FeynHiggs2.3.2. by S. Heinemeyer, W. Hollik, G. Weiglein. • MSSM H+ production cross sections: NLO pp->tH+ provided by T. Plehn • Most of the background NLO cross sections provided by John Campbell; MCFM package • Introductions in Higgs sections are written by • M. Spira for SM and MSSM • S. Heinemeyer and G. Weiglein for MSSM benchmark scenarios + rad. corrections for mh • D. Dominici for 5D RS and M. Raidal for Little Higgs model

  5. Layout • Introduction • Part I: Higgs boson searches in Standard Model • Part II: Higgs bosons searches in MSSM • if still have time, Part III: • Higgs searches in non SUSY models • Conclusions

  6. SM Higgs mass constraints from the data and theory Experiment SM theory Indirect constraints from precision EW data : MH < 260 GeV at 95 %CL (2004) MH < 186 GeV with Run-I/II prelim. (2005) MH < 166 GeV (2006, ICHEP06) The triviality (upper) bound and vacuum stability (lower) bound as function of the cut-off scale L “triviality” : Higgs self-coupling remains finite Direct limit from LEP: MH > 114.4 GeV

  7. Present Tevatron exclusion limit All CDF and DØ results now combined for the first time  mH Limit/SM (GeV)Exp. Obs. 115 7.610.4 130 10.1 10.6 160 5.03.9 180 7.5 5.8 Note: the combined result is essentially equivalent to one experiment with 1.3 fb-1, since both experiments have “complementary” statistics at low and high mass  we are indeed already close to the sensitivity required to exclude or “evidence” the higgs at the Tevatron ICHEP06

  8. NLO Mt from TeV 2005: Mt=172.7+/-2.9 GeV hep-ex/0507091 We use 175 GeV in PTDR

  9. SM Higgs boson couplings and Br. ratios Djouadi, Kalinowski, Spira tree level couplings v is vev of Higgs field = 246 GeV Right bottom plot includes uncertainties from the quark masses mt, mb, mc and as(MZ)

  10. Physics runs 2008-2009. First , we should “discover” Standard Model

  11. ~ 107-8 Z->ll, W->ln on tape for 10fb-1 J. Campbell, R.K. Ellis, D. Rainwater hep-ph/0308195 Z, W, tt cross sections and expected number of events after trigger in CMS with 10 fb-1 W/Z+nJ+X NLO predictions at LHC with cuts : pTl > 15 GeV |hl| < 2.4 pTj > 20 GeV |hj| < 4.5 DRlj > 0.4 DRll > 0.2 W/Z bb + X |hb| < 2.5 ~ 106 tt->m+X for 10 fb-1

  12. W/Z+nJets is very important background for Higgs at LHC Zbb,Zcc, Wbb, Wcc (W/Z+QQ+nj) are as important as W/Z+nj

  13. Part 1 SM Higgs boson searches. Rescaling for the light Higgs boson (h) in MSSM

  14. H->ZZ(*)->4l - golden mode of CMS(first studies in 1995) • Background: tt, ZZ, llbb (“Zbb”) • Selections : • lepton isolation in tracker and calo • lepton impact parameter, mm, ee vertex • mass windows MZ(*), MH H->ZZ->ee mm

  15. H->ZZ->4l • New elements of analysis: • ZZ background: NLO k factor depends on m4l • background from side bands or from ZZ/Z; (gg->ZZ is added as 20% of LO qq->ZZ, no generator yet) Signal and background at 5 sigma discovery eemm eemm CMS at 5s sign. CMS at 5s sign.

  16. H->ZZ->4l Signal significance: new vs old results; no big change ~ 125 GeV

  17. New: CP property with H->ZZ->4l d G (h) ~ H + h I + h2 A, H scalar, A – pseudoscalar, h=tan(x), x = +/- p/2 --> A C2 = s Br / sSM Br SM C2 needed to exclude SM h

  18. Inclusive H->gg CMS plot of the ECAL TDR time : December 1997 Went then from hybrid silicon + gas chamber tracker to all silicon tracker

  19. New elements of PTDR 2006 analysis: - splitting into categories depending of R9=E(3x3)/Esc and h regions - usage of LLR for discovery, systematic - “optimized analysis” – NN with kinematics and g isolation as input, s/b per event 1 fb-1 1 fb-1 barrel with large R9 barrel with small R9 1 fb-1 1 fb-1 endcaps with large R9 endcaps with small R9

  20. Discovery potential of H->gg SM light h->gg in MSSM inclusive search Significance for SM Higgs MH=130 GeV for 30 fb-1 * NN with kinematics and g isolation as input, s/b per event

  21. Accuracy of the Higgs boson mass measurement with H->ZZ->4l and H->gg Stat. error only

  22. Early discovery with H->WW->2l2n ...counting experiment... • New elements of analysis • PT Higgs and WW bkg. as at NLO (re-weighted in PYTHIA) • include box gg->WW bkg. • NLO Wt cross section after jet veto • Backgrounds from the data (and theory) • tt from the data; uncertainty 16% at 5 fb-1 • WW from the data; uncertainty 17% at 5 fb-1 • Wt and gg->WW bkg from theor. uncertainty 22% and 30% after cuts: - ETmiss > 50 GeV - jet veto in h < 2.4 - 30 <pT l max<55 GeV - pTl min > 25 GeV - 12 < mll < 40 GeV

  23. Discovery reach with H->WW->2l Excluded cross section times Branching Ratio at 95% C.L. CMS Phys. TDR 2006 very similar to old results w/o syst.

  24. Luminosity needed for 5 s discoveryfor incl. Higgs boson production

  25. (written in 2005)

  26. First, full simulation analysis ofqqH, H->tt->l+jet SM discovery light h in MSSM Discovery in Standard Model

  27. Summary of SM Higgs boson discovery: Signal Significance for 30 fb-1 with K factors ATLAS h->gg sensitivity is now comparable with CMS CMS ttH, H->bb does not have even 3 s with 60 fb-1

  28. Part 2 Higgs boson searches in Constrained MSSM

  29. Constraints on MSSM Higgs from LEP searches in mhmax scenario From hep-ex/0602042 mt= 169.3 174.3 179.3 183.0 Low tanb is not completely excluded: search for LHC with pp->A; A->Zh, gg, tt High tanb area for search at LHC with pp->bbf (f=h, H, A) and f->mm, tt decays

  30. Light SUSY Higgs in CPX (no CMS reach yet evaluated, ATLAS did scanning)

  31. CMS reach for MSSM neutral Higgs bosons • pp->bbf (f->h, H, A) – high tanb • f->mm • f->tt • pp->A at low tanb • A->Zh • Z->ll (l=e, m) • h->bb

  32. pp->bbf, f->mm Discovery reach at low MA, “intensive coupling” and decoupling regimes h+A H+A h+H+A Possible constraint on tanb by measuring width of A/H->mm

  33. pp->bbf, f->tt Tevatron f (f->tt) f=h, A, H CMS bbf (->tt, mm) f=h, A, H CMS Note 2003/033 plot below is updated (see next slides) ICHEP06 Exclusion Discovery/measurement

  34. Z->tt as benchmark for H->tt mass reconstruction Tevatron analysis of f->tt:Z->tt->l+jet is selected ! CDF Run II analysis; 310 pb-1; hep-ex/0508051 CMS, 2006 Z->tt->m+jet in CMS, 2006: S ~ 1000 ev, B: tt ~ 60 ev., W+j ~ 40ev. , bb ~ 60 ev. for 30 fb-1

  35. bbZ as benchmark for bbH kinematics Z+2 b-tagged jetsat CMS, 2006 Z + ≥1 b-tagged jetat Tevatron PRL 94, 161801 (2005) 1065 events under peak for 30fb-1 - 70 % signal bbZ - 11 % DY - 19 % tt~ pTb

  36. MSSM neutral Higgs bosons: TeV vs LHC CMS prospects for discovery Phys TDR 2006 CDF+D0 prospects

  37. tan(b) “measurement” with MSSM bbA Cross section (and width) exhibits a large sensitivity to tan(b) and thus can add a significant observable to a global fit of the SUSY parameters From cross section of A->tt From width measurement with A->mm • R. Kinnunen, S. Lehti, F. Moortgat, • Nikitenko, M. Spira. CMS Note 2004/027 • Need to be updated for PTDR 2006 results

  38. Access to low tanb with A/H->c20c20->4l + ETmiss • Background • SUSY, SM: tt, ZZ, Zbb • Selections: • Lepton isolation • Jet veto • ETmiss, pT4l < 80 GeV • Z veto Chosen points in mSUGRA Point C after selections

  39. Access to low tanb with A/H->c20c20->4l

  40. MSSM charged Higgs boson

  41. Selections 2006: ETmiss > 100 GeV ETtjet > 100 GeV t polarization: Rt = p ltr/Et jet > 0.8 Mtop + b tagging veto of 4th jet ETHiggs > 50 GeV

  42. The 5 s discovery reach of CMS 2003 for MSSM charged Higgs bosons with mhmax scenario. CMS Note 2003/033 NLO cross section for pp->tH-+X Gap at MH+ ~ Mt is artificial due to usage of gg->tt (NWA) cross section gg->tbH+ process is available in PYTHIA (S. Moretti et al. Les Houches 2003) NLO cross section is available. (T. Plehn et al., hep-ph/0312286)

  43. CMS reach in MA-tanbwith searches for charged Higgs boson CMS Phys. TDR 2006 Effect of systematic on discovery reach

  44. Summary of CMS reach in MA-tanb

  45. Can MSSM be distinguished from SM in the area of only light Higgs discovery ? discrepancy from the SM for light h M. Duhrssen et al.,hep-ph/04063232

  46. Part 3 Higgs boson searches in 5D RS model and Little Higgs model

  47. Free parameters of 5D Randall-Sundrum model: mf, mh, Lf, x (f-h mixing)

  48. Radion (f)->hh->ggbb, ttbb, bbbb search.motivation • CMS work by D. Dominici, G. Dewhirst, • Nikitenko, S. Gennai, L. Fano’ • CMS Note 2005/007 5D Randall-Sundrum model paramers: mf, mh, Lf, x • We fixed : • mf=300 GeV, mh=125 GeV • and scan in the • (x, Lf) plane • full simulation for signal: f->hh with • ggbb, ttbb, bbbb decay modes • fast simulation for background • MadGraph for • ggjj, ggcc, ggbb background • CompHEP for Zbb background • Signal with corrected PYTHIA • s, Br with modified HDECAY + HIGLU Lf = 2 TeV, mh = 125 GeV 30 fb-1 x f->ZZ->4l discovery no discovery for h->2g sBr(hSM->ZZ->4l) ~= sBr(f->ZZ->4l) mf, GeV X->hh discovery with ~ 30 fb-1 is a hint for radion

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