1. Higgs Physics with ATLAS Markus Schumacher, Bonn University Seminar über Teilchenphysik, Wuppertal, November 10th 2005

2. 2 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Outline u the Higgs Mechanism and SM Higgs phenomenology at LHC u discovery potential for SM Higgs boson u investigation of the Higgs boson profile u phenomenology of SUSY Higgs bosons u discovery potential for MSSM Higgs bosons u discriminating the SM from extended Higgs sectors u conclusion and outlook

3. 3 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 The Higgs Mechanism in the Nut Shell  consistent description of nature seems to be based on gauge symmetry  SU(2) L xU(1) gauge symmetry  no masses for W and Z and fermions  „ad hoc“ mass terms spoil The problem: The „standard“ solution: new doublet of complex scalar fields with appropiately choosen potential V  vacuum spontaneously breaks gauge symmetry  one new particle: the Higgs boson H = v + H renormalisibilty  no precise calculation of observables high energy behaviour  W L W L scattering violates unitarity at E CM ~1.2 TeV

4. 4 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Mass generation and Higgs couplings: = v + H  effective mass = friction of particles with omnipresent „Äther“ v =247 GeV x fermion gfgf m f ~ g f v Yukawa coupling M V ~ g v gauge coupling x x W/Z boson g gauge Interaction of particles with v=247 GeV Fermions g f ~ m f / v W/Z Bosons: g V ~ 2 M V / v Interaction of particles with Higgs H fermion gfgf x W/Z boson g gauge Higgs v 2 2 VVH coupling ~ vev only present after EWSB breaking !!! 1 unknown parameter in SM: the mass of the Higgs boson

5. 5 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 bW ZZ tt  cc gg  Higgs Boson Decays in SM for M<135 GeV: H  bb, dominant for M>135 GeV: H  WW, ZZ dominant tiny: H   also important HDECAY: Djouadi, Spira et al.

6. 6 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Status of SM Higgs Searches I: LEP M H < 186 GeV at 95% CL,m top =172 GeV (M H <216 GeV for m top =175 GeV) M H <114.4 GeV excluded at 95% CL Direct search: Electroweak fit:

7. 7 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Status of SM Higgs Searches II: TEVATRON Expected sensitivity: 95% CL exclusion up to 130 GeV with 4fb -1 per experiment 3 sigma evidence up to 130 GeV with 8fb -1 per experiment Current sensitivity:: Cross section limits at level of ~ 10 x SM cross section

8. 8 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 1)mass 2)quantum numbers: spin and CP 3)BRs, total width, couplings 4)self coupling at SLHC Higgs Physics at LHC  discovery of 1 neutral scalar Higgs boson (determination of mass, spin, CP)  discrimination between SM and extended Higgs sectors 1)> 1 neutral Higgs boson 2)charged Higgs boson 3)exotic decay modes e.g. H  invisible 4) … … … direct observation of additional Higgs bosons determination of Higgs profile: deviations from SM prediction

9. 9 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 LHC and ATLAS  LHC: proton proton collisions at E CM = 14 TEV, start in 2007 - low luminosity running: 1(2)x10 33 /(cm 2 s)  10(20) fb -1 /year - high luminosity running: 10 34 /(cm 2 s)  100 fb -1 /year  A Toroidal LHC Aparatus design optimised for low mass Higgs boson discovery: H  2 photons, H  ZZ  4 leptons anticipated  M /M H ~ 1 %  em.-calorimetry, spectrometer ttH, H  bb  b =60(50)% R c >10 R udsg >100  Si tracking detectors H  tau tau,  WW  ll, VBF prod. missing E. resolution, hermiticity, forward jets  calorimetry to  = 5  MC studies with fast simulation of ATLAS detector  key performance numbers from full sim.: b/tau/jet/el.// identification, isolation criteria, jet veto, mass resolutions, trigger efficiencies, …

10. 10 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Production of the SM Higgs Boson at LHC

11. 11 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 QCD corrections and Knowledge of Cross Sections  K =  NNLO / LO ~2   = 15% from scale variations  error from PDF uncertainty ~10% Caveat: scale variations may underestimate the uncertainties! ttH: K ~ 1.2 ~ 15% WH/ZH: K~1.3 to1.4 ~7% VBF: K ~ 1.1  ~ 4% + uncertainties from PDF (5 to 15%)  but: rarely MC at NLO avaiable (except gluon gluon fusion)  background: NLO calculations often not avaiable  need background estimate from data  ATLAS policy: use K=1 for signal e.g.: Gluon Gluon Fusion Harlander et al.

12. 12 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Cross sections for Background Processes Higgs 150 GeV: S/B <= 10 -10 overwhelming background  trigger: 10 -7 reduction on leptons, photons, missing E p p q q q pp q q q q H WW l l Background: mainly QCD driven Signal: often electroweak interaction  photons, leptons, … q

13. 13 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Discovery Potential for light SM Higgs boson discovery channels  GGF: H    GGF: H  ZZ  4l +-  GGF: H  WW  2(l)  ttH: H  bb  VBF: H    VBF: H  WW For M H >300 GeV also: VBF: H  ZZ  ll VBF: WW  lqq  no fully hadronic final states: eg. GGF, VBF: H  bb  Higgs Boson mass reconstruction possible?  background controlable (S/B), estimate from data possible? excluded by LEP For M H >330 GeV also: VBF: H  ZZ  ll VBF: WW  lqq excluded by LEP since 2000

14. 14 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 H  2 Photons ATLAS  signature: two high P t   background: irreducible pp   +x reducible pp  j, jj, …  exp issues (mainly for ECAL): , l +-,  0 separation (jet fake rate 10 -4 ) - energy scale, angular resolution - conversions/dead material mass resolution  M : ~1% precise background estimate from sidebands (O(0.1%)) S/BG ~ 1/20 ATLAS 100fb -1

15. 15 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Gluon Fusion: H  ZZ (*)  4 Leptons  signature: 4 high p t isolated leptons 1(2) dilepton mass ~ M Z  irreducible BG: ZZ  mass reconstruction  reducible BG: tt, Zbb  4 leptons  rejection via lepton isolation and b-veto ATLAS TDR  good mass resolution  M : ~1%  small and flat background  easy estimate from data

16. 16 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Gluon Fusion: H  WW  l l ATLAS M=170GeV L=30fb -1  signature: - 2 high p t leptons + large missing E T - lepton spin corrleations - no mass peak  transverse mass transverse mass  BG: WW, WZ, tt lepton iso., missing E resolution jet (b-jet) veto against tt  BG estimate in data from  ll  NLO effect on spin corr.  gg  WW contribution signal like Dührssen, prel.  ll

17. 17 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 ttH with H  bb  mass resolution  M : ~ 15%  50% correct bb pairings  very difficult background estimate from data with exp. uncertainty ~ O(10%)  normalisation from side band  shape from „re-tagged“ ttjj sample  reducible BG: tt+jets, W+jets  b-tagging irreducible BG: ttbb  reconstruct mass peak  exp. issue: full reconstruction of ttH final state  combinatorics !!! need good b-tagging + jet / missing energy performance S/BG ~ 1/6 30 fb -1 only channel to see H  bb ATLAS  signature: 1 lepton, missing energy 6 jets of which 4 b-tagged

18. 18 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Vector Boson Fusion: pp  qqH Jet  signature: -2 forward jets with large rapidity gap - only Higgs decay products  in central part of detector   Forward tagging jets Higgs Decay

19. 19 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Vector Boson Fusion: pp  qqH  2 forward tagging jets with rapidity gap: p T >20GeV forward jet reconstruction ATLAS High Lumi Low Lumi jet-veto fake rate due to pile up ATLAS  theory questions: jet distributions at NLO? esp. direction of 3rd jet? efficieny of central jet veto?  need NLO MC generator for signal and BG  experimental issues:  

20. 20 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005  signature: tagging jets + - 2 high p t leptons + large missing E T - lepton spin corrleations (spin1  0) - no mass peak  transverse mass Weak Boson Fusion: H  WW  ll (lqq) tt, Wt, WWjj,...  backgrounds: H  WW  e ATLAS 10 fb -1 M H =160 GeV  S/BG ~ 3.5/1  BG uncertainty ~ 10 % shape from MC normalisation from side bands in M T and  ll central jet veto b-veto

21. 21 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 ATLAS H    e  Vector Boson Fusion: H  tau tau  ll 4 (l had 3 )  mass resolution ~ 10% determined by missing E. resolution  BG uncertainty ~ 5 to 10% for M H > 125 GeV: flat sideband for M H < 125 normalisation from Z peak 30 fb -1 M H =120 GeV  signature: tagging jets + - 2 high p t leptons + large missing E T - mass reconstruction despite 4 in collinear approximation  backgrounds: Zjj, tt S/BG ~ 1 to 2 / 1 central jet veto reconstruction of m 

22. 22 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Vector Boson Fusion, H  estimate of BG shape from data  Idea: jjZ  andjjZ     look almost the same esp. in calos  same missing energy only momenta different  Method: select Z   events randomise momenta apply „normal“ mass reco. PT miss,final (GeV)M  (GeV) promising prel. results from ongoing diploma thesis in BN (M. Schmitz)

23. 23 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 SM discovery potential depending on int. luminosity excluded by LEP discovery from LEP exclusion until 1 TeV  from combination of search channels with 15 fb -1 of well understood data  with individual search channels with 30 fb -1 of well understood data

24. 24 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Investigation of Higgs boson profile 1) Mass  determines completly SM phenomenology 2) Spin and CP QN  Is it a CP even scalar boson? 3) Couplings  Is it responsible for mass generation? test SM prediction with best accuracy look for deviations  hint towards new physics

25. 25 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Measurement of Higgs Boson Mass ATLAS M/M: 0.1% to 1%  Uncertainties considered:  “Indirect” from Likelihood fit to transverse mass spectrum: H  WW  ll WH  WWW  lll  Direct from mass peak: H  H  bb H  ZZ  4l VBF with H   or WW not studied yet ! i) statistical ii) absolute energy scale 0.1 (0.02) % for l,,1% for jets iii) 5% on BG + signal for H  WW

26. 26 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005  sensitivity through spin correlations of Higgs decay products  one possibility H  ZZ  4 leptons Spin and CP Quantum Numbers: 0 even in SM : angle btw. decay planes :angle btw. leptons and Z in Z rest frame (Gottfried Jackson angle) Higgs rest frame  observation of H  or gg  H rules out Spin=1 (Young theorem) L (T) ratio of longitudinal (tranverse) polarised Z bosons 100 fb -1

27. 27 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Spin and CP Quantum Numbers: discrimination power  alternative methods: decay: H   via spin correlations production: i) ttH angle between t,t,H ii) VBF  btw. tagging jets        discrimination dominated by  for masses > 250 GeV  seperation power > 2  for all spin, CP hypothesis and M H >200 GeV  currently under study: - NLO effects - verification with full sim. + all BGs - lower masses H  ZZ*

28. 28 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Determination of Higgs boson couplings Loop induced effective couplings: (sensitive to new physics) Photon: g  = g W “+“ g t “+“… Gluon: g  = g t “+“ g b “+“… H x x Born level couplings: Fermions g f = m f / v W/Z Bosons: g V = 2 M V / v 2  couplings in production  Hx = const x  Hx and decay BR(H  yy) =  Hy /  tot  experiment: rate = N sig +N BG N sig = L x efficiency x  Hx x BR  need to know: luminosity, efficiency, background  Hx x BR ~  HX  Hy  tot prod decay partial width:  Hz ~ g Hz 2  tasks: - disentangle contribution from production and decay - determine  tot

29. 29 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005  ratios of BRs = ratios of  = ratios of g, if only Born level couplings e.g. 9 fit parameters: all rates can be expressed by those 9 parameters H  WW chosen as reference as best measured for M H >120 GeV For 30fb -1 worse by factor 1.5 to 2 13 analysis used Ratio of Partial Widths   including various exp. and theo. errors

30. 30 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Total Decay Width  H  for M H >200 GeV,  tot >1GeV  measurement from peak width in ZZ  4 l  upper limit needs input from theory: mild assumption: g V <g V SM valid in models with only Higgs doublets and singlets rate(VBF, H  WW) ~  V 2 /  tot < ( V 2 in SM)/  tot   tot < rate/( V 2 in SM)  lower limit from observable rates:  tot >  W + Z + t + g +....  for M H <200 GeV,  tot << mass resolution  no direct determination  have to use indirect constraints on  tot

31. 31 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Absolute couplings with g V < g V SM constraint  coupling to W, Z, , b, t g/g = ½ g 2 )/g 2   inv for undetactable decays e.g. c, gluons,new   photon (new),  gluon (new): non SM contribution to loops g/g = ½ g 2 )/g 2

32. 32 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 M H 2 =  2 =M Planck Motivation for Supersymmetry from Higgs Sector  Higgs problem in SM: large corrections to the mass of the Higgs-Boson 2  “solves” hierarchy problem: why v = 246 GeV << M Pl =10 19 GeV ? M H 2 = (M SM- M SUSY ) 22 WW + H H  natural value ~ M Pl  electroweak fit M H ~O(100GeV)  SUSY solution: - partner with spin difference by ½ cancel divergence exactly if same M - SUSY broken in nature, but hierarchy still fine if M SUSY ~1 TeV H H   -  SUSY breaking in MSSM: parametrised by 105 additional parameters too many  constrained MSSM with 5 (6) additional parameters

33. 33 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 The MSSM Higgs sector in a tiny Nut Shell  SUSY: 2 Higgs doublets  5 physical bosons real MSSM: 2 CP even h, H, 1 CP odd A, charged H +, H -  at Born level 2 parameters: tan, m A m h < M Z  large loop corrections from SUSY breaking parameters m h < 133 GeV for m top =175 GeV, M SUSY =1TeV  corrections depend on 5 SUSY parameters: X t, M 0, M 2, M gluino,  fixed in the benchmark scenarios e.g. MHMAX scenario  maximal M h  conservative LEP exclusion  t b/ W/Z h cossin-sincossin() H sinsincos/coscos() A cottan -----  g MSSM = g SM no coupling of A to W/Z small   small BR(h  ,bb) large    large BR(h,H,A  ,bb)  = mixing btw. CP-even neutral Higgs bosons

34. 34 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Discovery Potential in the tanversus M A Plane  LEP tan exclusion: no exclusion for m t larger ~183 GeV !  TEVATRON: so far exclusion for tan > 50 M A <200GeV  calculations with FeynHiggs (Heinemeyer et al.)  no systematic uncertainties yet main questions for ATLAS:  At least 1 Higgs boson observable in the entire parameter space?  How many Higgs bosons can be observed?  Can the SM be discriminated from extended Higgs sectors? 4 CP conserving benchmark scenarios considered: Carena et al., Eur.Phys.J.C26,601(2003) 1)MHMAX 2) No mixing 3) Gluophobic 4) small  conclusions the same due to to complementarity of search channels M top =174.3 GeV

35. 35 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 h or H observable with 30 fb -1 Vector Boson Fusion: 30 fb -1 studied for M H >110GeV at low lumi running

36. 36 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Light Higgs Boson h  large area covered by several channels   sure discovery and parameter determination possible  small area uncovered @ m h ~ 95 GeV 300 fb -1 30 fb -1  VBF dominates observation  small area from bbh,H   for small M h

37. 37 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Heavy Neutral Higgs Bosons large tan: bbH/A, H/A   ~ (tan) 2 ATLAS 30fb -1 low mass<450GeV:   lep. had. trigger on lepton large mass > 450GeV: also   had. had. larger rate, trigger on hard tau jets Eff.(LV1TR)= 80% =95% offline selected events Tau ID: eff(tau)=55% rejection(QCD)=2500 H/A  

38. 38 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Overall Discovery Potential: 300 fb -1  at least one Higgs boson observable for all parameters in all CPC benchmark scenarios  significant area where only lightest Higgs boson h is observable  questions for future studies: can SUSY decay modes provide observation? e.g.: H/A       2 LSP + 4 lept. ongoing study in BN (N. Möser) similar results in other benchmark scenarios VBF channels, H/A  only used with 30fb -1 300 fb -1

39. 39 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 ATLAS prel. 300 fb -1 SM or Extended Higgs Sector e.g. Minimal SUSY ? discrimination via rates from VBF R = BR(h  WW) BR(h  )  assume Higgs mass well measured  no systematic errors considered compare expected measurement of R in MSSM with prediction from SM for same value of M H =|R MSSM -R SM | exp

40. 40 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 The Higgs Sector in the CP Violating MSSM mass eigenstates H 1, H 2, H 3 <> CP eigenstates h,A,H  at Born level: CP symmetry conserved in Higgs sector  complex SUSY breaking parameters introduce new CP phases  mixing between neutral CP eigenstates  no a priori reason for real SUSY parameters  complex pars.  new sources of CP violation  el.-weak baryogenesis in complex MSSM ok  evade constraints from dipole moments via cancellations of different terms or split SUSY Why consider such scenarios? M. Carena, M. Quiros, C.Wagner’98

41. 41 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Phenomenology in the CPX scenario  H 1,H 2, H 3 couple to W,Z  all produced in VBF H3 H2 H1  H 2,H 3  H 1 H 1, ZH 1, WW, ZZ decays possible  no limit for mass of H 1 from LEP (compare CPC MSSM: M h >M Z  maximise effect  CPX scenario (Carena et al., Phys.Lett B495 155(2000)) arg(A t )=arg(A b )=arg(M gluino )=90 degree  scan of Born level parameters: tan and M H+- LHWG-Note 2004-01

42. 42 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 CP-Violating MSSM: Overall Discovery Potential M H1 : < 70 GeV M H2 : 105 to 120 GeV M H3 : 140 to 180 GeV small masses below 70 GeV not yet studied in ATLAS 300 fb -1  most promising channel: tt  bW bH +, H +  W H 1, H 1  bb final state: 4b 2j l same as ttH, H  bb (study in Bonn)  revised studies for H 2/3  H 1 H 1 also interesting  yet uncovered area  size and location of „hole“ depends on M top and program for calculation

43. 43 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Very First look at new promising MC study M H+ =135 GeV, M H1 =54GeV, tan=4.8 (diploma thesis M. Lehmacher)  estimate of background seems difficults  coverage of hole area under study! signal ttjj ttbb  t t  H + b W b H +  W H 1 H 1  bb  1 leptonic W decay  lepton for trigger  reconstruct top quarks  combinatorics  associate b quarks to H 1, H +  M H1 and M H+

44. 44 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Conclusion and Outlook  Standard model: discovery of SM Higgs boson with 15 fb -1 requires good understanding of whole detector multiple channels with larger luminosity  Higgs profile investigaton  CP conserving MSSM: at least one Higgs boson observable only h observable in wedge area at intermediate tan maybe Higgs to SUSY or SUSY to Higgs observable? discrimination via Higgs parameter determination seems promising  CP violating MSSM: probably a „hole“ with current MC studies promising MC studies on the way  more realistic MC studies: influence of miscalibrated and misaligned detector improved methods for background estimation from data use of NLO calcluations and MCs for signal and background  additional extended models + seach channels: CPV MSSM, NMSSM, 2HDM Higgs  SUSY, SUSY  Higgs VBF, H  bb (b-trigger at LV2), VBF,H  inv. (add. forward jet trigger)

45. 45 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Let‘s wait and work for Higgs boson discovery …. Thanks for your attention!

46. 46 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Backup slides

47. 47 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Evidence for Spin 0 in H->WW->ll mode  between leptons W from H opposite spins  leptons same direction + add. BG normalisation M T >175 GeV M T <175 GeV Signal Region Outside Signal Region Background estimate for VBF, H  WW m T (ll) with (left) and w/o (right) lepton cuts  background estimation at level of 10% from data + shape from MC ATLAS Transverse mass

48. 48 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 CP even Spin 0: Measurement of Rates Simultaneous fit of signal rates x BR in all 13 channels Takes into account:  cross talk between channels (e.g. GF events selected in VBF analysis)  statistical fluctuations  detector effects:  Lumi,  eff. tau, b-, forward jet tagging,  and e  background estimates: sidebands + shape + theoretical prediction  uncertainties to signal rate from PDFs and QCD corrections

49. 49 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Overview of 13 Channels used in new ATLAS Study ProductionDecayMass range Gluon fusion H   H  ZZ  4l H  WW (*)  l l 110 – 150 GeV 120 – 200 GeV 110 – 200 GeV Vector Boson Fusion* H   H   H  WW (*)  l l H  ZZ  4l 110 – 150 GeV 110 – 150 GeV 110 – 190 GeV 110 – 200 GeV ttH H   H  bb H  WW  l l 110 – 120 GeV 110 – 140 GeV 120 – 200 GeV WH H   H  WW  l ll 110 – 120 GeV 150 – 190 GeV ZH H   110 – 120 GeV * only studied for low lumi running, L= 30fb -1

50. 50 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Higgs  invisible particles need confirmation by full simulation study VBF assumes trigger on forward jets, not yet implemented

51. 51 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Higgs self coupling

52. 52 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 The four CPC Benchmark Scenarios Carena et al., Eur.Phys.J.C26,601(2003 )  Gluophobic scenario small g h,gluon m h < 119 GeV  Small  scenario  small g hbb and g h m h <123 GeV  MHMAX scenario maximal m h < 133 GeV  conservative LEP exclusion  Nomixing scenario small m h < 116 GeV  difficult for LHC theo. goal: harm discovery via gg  h, h   and h  ZZ  4 l theo. goal: harm discovery via VBF, h   tth, h  bb

53. 53 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Signal and Background Rates  LO with CTEQ5L (no K-factors!)  running b-quark mass for bbh(/H/A) and gb  tH + 1) SM production cross sections times MSSM correction factors (FH) 2) branching ratios from FeynHiggs 3) efficiencies and background expectations from documented MC studies  M t = 175 GeV used for now

54. 54 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 4) for part of MSSM parameter space: large  tot   MSSM = K  SM K = Corrections to Expected Signal Rates 5) signal overlap due to mass degeneracy of Higgs bosons count signal in mass window 1 = signal 1 + signal 2 in window 1 h

55. 55 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 MC Studies with Discovery Potential channellumimass rangepublication VBF, H  WW lowM>110 GeV SN-ATLAS-2003-024 ttH, H  bb *low+highM>70GeV ATL-PHYS-2003-003 bbH/A   low+high70<M<135GeV M> 120 GeV ATL-PHYS-2002-021 ATL-PHYS-2000-005 bbH/A    lep.had   had. had. low M >120 GeV M > 450 GeV ATL-PHYS-2000-001 ATL-PHYS-2003-009 ATL-PHYS-2003-003 WW  ll low+high140<M <120GeV ATL_PHYS-2000-015 H   low+highM > 70 GeV TDR ZZ  4llow+highM > 100 GeV TDR A  Zh  llbb, H  hh  bb low+high60 <ML<130 100<MH<360TDR H/A  ttlow+highM > 350 GeV TDR gb  tH+-, H  ,tb low+highM >180 GeV SN-ATLAS-2002-017 tt  bW bH+-, H+-   lowM < 170 GeV ATL-PHYS-2003-58/TDR * ttH, H  bb at high. lumi see MSSM note

56. 56 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 almost same conclusion for all 4 CP conserving benchmark scenarios Vector Boson Fusion: 4 CPC scenarios

57. 57 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Light Higgs Boson h: 30 fb -1  difference mainly due to different m h in same (tan,M A ) point ( up to 17 GeV difference) observable channels: VBF bbh h   tth h  bb

58. 58 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Small  scenario, h: 30 fb -1 covered by enhanced BR to gauge bosons complementarity of search channels almost gurantees observation of h hole due to reduced branching ratio for H  

59. 59 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Light Higgs Boson h: 300 fb -1 (VBF only 30 fb -1 )  also h  gg, h  ZZ  4 leptons, tth  bb contribute  large area covered by several channels  sure discovery and parameter determination possible  small area uncovered @ m h = 90 to 100 GeV  h  sensitive in gluophobic scenario due to Wh, tth production

60. 60 Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 Charged Higgs Bosons gb  H +- t H +-   t  bqq low mass: m H+- < m top gg  tt tt  H +- bW only low lumi. new: W  qq H +-   high mass: m H+- > m top  transition region around m top needs revised experimental analysis  running bottom quark mass used  Xsec for gb  tH +- from T. Plehn‘s program