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Higgs Search at LHC (and LHC/CMS status)

Higgs Search at LHC (and LHC/CMS status). Andrey Korytov (for ATLAS and CMS Collaborations). ATLAS CMS. Outline. LHC status CMS Experiment status Standard Model Higgs boson MSSM Higgs bosons.

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Higgs Search at LHC (and LHC/CMS status)

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  1. Higgs Search at LHC(and LHC/CMS status) Andrey Korytov (for ATLAS and CMS Collaborations) ATLAS CMS

  2. Outline • LHC status • CMS Experiment status • Standard Model Higgs boson • MSSM Higgs bosons

  3. LHC status and plans

  4. LHC status • LHC sectors are being cooled down the last sector “45” will be at ~2K in July • Some magnets need additional training to reach Bmax • To have the beam this year, LHC will start out at 10 TeV (no additional training needed) • Magnets will be re-trained during winter shutdown to allow for the 2009 run at 14 TeV T~2K, ready for “cold tests”, commissioning, and beam

  5. LHC plan for 2008-2009 • 2008 • beam commissioning Aug-Oct • center-of-mass energy 10 TeV (some magnets need further training) • peak luminosity 51031 cm-2s-1 • physics run 40 days (Oct-Nov) • overall efficiency* 0.1 (based on the 1st year of LEP1) • integrated luminosity 20 pb-1 (delivered for physics) • 2009 • center-of-mass energy 14 TeV • peak luminosity 1033 cm-2s-1 • physics run 150 days (May-Nov) • overall efficiency* 0.2 (based on subsequent years of LEP1) • integrated luminosity 2.5 fb-1 (delivered for physics)

  6. CMS commissioning status

  7. CMS experiment status • Muon System • Solenoid • Hadron Calorimeters • EM Calorimeter • Tracker

  8. CMS Magnet • Parameters: • superconducting • 4 Tesla • diameter 6 m • length 13 m • stored energy 2.6 GJ • 64 Bar Radial Pressure • Status: • fully tested while still on surface • cold and ready to be energized • initial field will be 3.8 T

  9. CMS Tracker • Parameters: • coverage |h|<2.5 • diameter 2.2 m, length 6 m • 220 m2 sensitive area (more than all HEP experiments combined) • Strips: 11M channels (cf. CDF <1M) 20-80 mm precision measurements • Pixels: 66M channels 15 m precision measurements • Status: • Strip Detector: fully commissioned on surface (good strips ~99.9%) installed to be operational by mid-July • Pixel Detector: ready for installation in June

  10. EM Calorimeter • Parameters: • barrel + endcaps: |h|<2.5 • 76K PbWO4 crystals and readout channels (more crystals—in volume or number—than in all previous HEP experiments combined) • Status: • barrel: installed, commissioned pre-calibrated to 2% • one endcap: to be installed in mid-June • second endcap: ready by mid-July (install if LHC schedule allows)

  11. CMS Hadron Calorimeter • Parameters: • barrel/endcap |h|<3: copper + scintillator • forward 3<|h|<5: steel + quarts fibers • ~10K channels • Status: • installed, commissioned • calibrated to 5% Jet Energy Resolution

  12. CMS Muon System • Status: • all 100% installed • DTs: 85% fully commissioned • CSCs: 50% fully commissioned • RPCs: 10% fully commissioned • all to be commissioned by mid-July • Parameters: • coverage |h|<2.4 • Barrel: Drift Tube chambers • Endcap: Cathode Strip Chambers • Resistive Plate Counters throughout • 26,000 m2 sensitive area • 700K readout channels • ~100 mm resolution per chamber RPCs (barrel+endcaps) CSCs (endcaps: 8 disks) Drift Tubes (barrel: 5 wheels)

  13. HCAL ECAL Tracker HCAL MUON Cosmic Muon Events in CMS • May 2008 • underground, B=0 T • August 2006 • on the surface, B=3.8 T • (not all detectors on) HCAL ECAL

  14. Cosmic Ray Muons on surface • Magnet Test and Cosmic Challenge in 2006-07 • Magnet reliably operates at 3.8 T • Fraction of all sub-detectors were operational • Many million cosmic ray events were collected • Cosmic ray muons were successfully reconstructed, including their momenta, charge ratio, etc.

  15. Cosmic Ray Muons underground • photograph: one of the endcap • muon system stations • occupancy plot: muon hits • registered in that station

  16. Higgs search prospects More details are in parallel session talks: SM Higgs boson with ATLAS (Francesco Polci) SM Higgs boson H 2g with CMS (Serguei Ganjour) SM Higgs boson H ZZ(*) and WW(*) with CMS (Sinjini Sen Gupta) SM Higgs boson produced in VBF with ATLAS (Guilherme Hanninger) SM Higgs boson produced in VBF with CMS (Pietro Govoni) SM Higgs boson in associated production mode with ATLAS (Huaqiao Zhang) MSSM Neutral Higgs bosons with ATLAS (Jana Schaarschmidt ) MSSM Neutral Higgs A/H 2m and 2t with CMS (Georgios Anagnostou) MSSM Charged Higgs bosons with ATLAS (Christopher Potter)

  17. SM Higgs: what we know from theory • One pseudo-scalar doublet F (4 degrees of freedom) • Potential V = l|F|4 - m2|F|2 • After spontaneous symmetry breaking: • W± and Z acquire masses (3 degrees of freedom) • the last remaining degree of freedom (4-3=1): scalar CP-even Higgs of unknown mass • l runs with Q: • small mH at 1-TeV scale • at some Q, l(Q) < 0 • V has no minimum (vacuum breaks loose) • large mH at 1-TeV scale • at some Q, l(Q) =  • theory is non-perturbative (theorists retire) • chimney • l(Q) ~ const due to cancellation of • +/- terms (fine tuning) • mass must be within 50-600 TeV range

  18. What we know experimentally: LEP Direct search at LEP: mH>114.4 GeV @ 95%CL

  19. What we know experimentally: EWK fits EWK precision data: mH<160 GeV @ 95%CL Combined with the direct search exclusion <114 GeV mH<190 GeV @ 95%CL

  20. projected Lint = 5-7 fb-1 by the end of 2009 What we know experimentally: Tevatron Note for the range around mH~160 GeV: The fact the currently observed limit runs ahead of the expected limit (left plot) makes it less likely to observe a 3s-excess later (right plot does not include these effects)

  21. SM Higgs at LHC • Colored cells = { detailed studies available } • YES = { discovery in the appropriate range of masses at L<30 fb-1 } uncertainties ~few % uncertainties ~5-20%

  22. 2003 Forerunners: analyses to see the Higgs first 2006 • ATLAS is coming up with many major updates now K factors included

  23. SM Higgs: Hgg • Backgrounds: • prompt gg • prompt g + jet(brem g, p0g) • dijets • CMS-2006 analysis: • cut-based • events sorted by “em shower quality” • kinematics, isolation, Mgg-peak • optimized • loose sorting and kinematical cuts • event-by-event kinematical Likelihood Ratio with bkgd pdf taken from sidebands, signal pdf from MC • systematic errors folded in CMS 2006 ATLAS 2006 S=6 @ L=30 agree

  24. 2008 2008 2003 SM Higgs: VBF, Htt • Backgrounds: • Zjj, tt • ATLAS-2008 analysis: • two forward jets, central jet veto • two leptons (e, m, or t-jet) and MET • inv. mass mtt built from l, (l or t-jet), and pTmis in collinear approximation (works quite well, despite multiple neutrinos present) • now qqH, Htt is • gives significance below 5s (despite including KNLO) • Htt is behind Hgg • ATLAS and CMS now agree m t pTmis t H m

  25. SM Higgs: HWW2l2n Signal Region Control Sample • Backgrounds: • WW, tt, Wt(b), WZ, ZZ • ggWW (box) • CMS-2006 analysis: • KNLO(pTWW) • cuts: • e/m kinematics, isolation, jet veto, MET • counting experiment, no peak • background from a control sample: • signal: 12<mll<40 GeV • control sample: mem>60 GeV • reduce syst. errors, but pay stat. penalty • systematic errors are folded in • 2008: updates expected from ATLAS and CMS CMS 2006

  26. jet f jet h SM Higgs: VBF, HWW2l2n Signal Region Control Sample • Backgrounds: • tt, WWjj, Wt • Old ATLAS Analysis: • 2 high pT leptons + MET • 2 forward jets (b-jet veto) • central jet veto • counting experiment, no peak • background from data: • Signal: all cuts • Control sample: no lepton cuts • Result: better than inclusive WW • 2008: updates expected from ATLAS and CMS ATLAS MH=160 GeV HWWe

  27. SM Higgs: HZZ4l CMS 2006 H ZZ4m • Backgrounds: • ZZ, Zbb, tt • CMS-2006 analysis: • NLO cross sections • ZZ: • 4-lepton mass dependent KNLO(m4l), <K>~1.35 • NNLO ggZZ box diagram, ~0.2 wrt LO • cuts: • isolation, vertex, e/m kinematics, m4l peak • control samples for ZZ background: • Z-peak (Z and ZZ production are very similar) - preferred • sidebands (low statistics, shape is not trivial) • Data-driven methods to measure • lepton reconstruction efficiency • isolation cut efficiency per event • vertex cut efficiency per event • full treatment of systematic errors (small effect) • for a broad search in a 110-600 GeV mass window, the “look elsewhere” effect de-rates significance by about 1 unit • 2008: updates expected from ATLAS and CMS CMS 2006

  28. SM Higgs: ttH, Hbb ttH is (was?) the best bet to see Hbb • Early projections: might be observable already at L=30 fb-1 • CMS-2006 analysis: • systematic error control at a percent level is needed—not feasible... • ATLAS-2008 analysis: • same conclusions mH = 120 GeV L = 30 fb-1 2008 2008 mH = 120 GeV L = 30 fb-1 CMS 2006 L=60 fb-1 ttH, Hbb current estimate of background uncertainties jet energy scale (3-10%) jet energy resolution (10%) b/c-tag efficiency (4%) uds/g-tag efficiency (10%) luminosity (3%)

  29. CMS 2006 NLO cross sections Systematic errors included Standard Model Higgs: Summary ATLAS update should become available this year CMS+ATLAS will need approximately half-luminosity in comparison to a single experiment • Benchmark luminosities (CMS+ATLAS): • 0.1 fb-1: exclusion limits will start carving into SM Higgs cross section • 0.5 fb-1: discoveries become possible if MH~160-170 GeV • 5 fb-1: SM Higgs is discovered (or excluded) in full range

  30. MSSM Higgs: what we know from theory • One doublet of Higgs pseudo-scalar fields is replaced with two • one couples to up-fermions and has vev=vu • the other to down-fermions and has vev=vd • which allows for cancellation of the higgsino triangular anomaly loops • 2x4-3=5 physical scalar fields/particles: h, H, A, H± • properties at tree level • fully defined by 2 free parameters: mA, tanb=vu/vd • CP-odd A - never couples to Z and W: - decays: bb, tt (and tt for small tanb) • CP-even h and H are - SM-like in vicinity of their mass limits vs mA - large tanb … enhances coupling to “down” fermions: b/t become very important! … suppresses coupling to Z and W • H± “strongly” couples to tb and tn • all Higgs bosons are narrow (G<10 GeV)

  31. MSSM Higgs: what we know from theory • Loop corrections give sensitivity to • the rest of SUSY sector • Special benchmark points*: • max stop mixing (mh-max): • maximizes mh • mh < 133 GeV • LEP results are least restrictive • no mixing: • opposite extreme to above • mh < 116 GeV • gluophobic h • ggh production is suppressed (top+stop loop cancellation) • mh < 119 GeV • small aeff (mixing of Fu/Fd): • htt and bb BR’s are suppressed even for large tanb • mh < 123 GeV *Suggested by Carena et al., Eur.Phys.J. C26, 601(2003)

  32. What we know experimentally: LEP (1) mh-max scenario makes LEP results least restrictive dotted line – expected limit light green – 99% CL, dark green – 95% CL yellow – theoretically not accessible

  33. What we know experimentally: LEP (2) 90 GeV mh-max scenario makes LEP results least restrictive dotted line – expected limit light green – 99% CL, dark green – 95% CL yellow – theoretically not accessible

  34. What we know experimentally: Tevatron tanb~40

  35. MSSM Higgs boson: h, H, A production h H A • x-sections are comparable or larger than SM (dotted line) • bb(h/H/A) productionis very important tanb=3 h H A tanb=30

  36. MSSM Higgs: SM-like signatures • ATLAS-2003: • no systematics included • updates are coming out this summer • CMS-2006: • better detector simulation • systematic errors included • contours recessed w.r.t. earlier projections 2006 ATLAS

  37. MSSM Higgs: heavy neutral H, A (F) • given the H/A mass degeneracy, they are often referred to as F • production in association with bb (especially good at large tanb) • Decays (large tanb): • bb-decay mode (~90%) is overwhelmed with QCD background • tt-decay mode (~10%) is the best bet • mm-decays (~0.03%) allow for direct measurement of G bbF, Fbb bbF, Ftt bbF, Fmm CMS, 60 fb-1 mh-max mA=600 GeV tanb=50 bbF, Fbb signal mbb(GeV)

  38. ATLAS MSSM Higgs: heavy neutral H, A (F) CMS 2006

  39. MSSM Higgs: Heavy H± • Heavy H± (M>mtop): • production via ggtbH± and gbtH± • tjjb • H± tb (BR~80%) overwhelmed by bkgd • H± tn (BR~20%) • backgrounds: tt+jets, tW+jets, W+jets H± tb and t(jjb or lnb) CMS H±tb

  40. MSSM Higgs: Light H± • Light H± (M<mtop): • production via plain qq/ggtt • tjjb • tbH± (depends on mass and tanb) H± tn (BR~100%) tt-jet (best channel) • main backgrounds: tt

  41. MSSM Higgs: H± summary

  42. ATLAS L=300 fb-1 Combining all together… • MSSM Higgs or SM Higgs? • SM-like h only: • considerable area… • even at L=300 fb-1 • Any handles? • measure branching ratios? • decays to SUSY particles? • SUSY particle decays?

  43. MSSM Higgs or SM Higgs? • BR for different channels: • R = BR(hWW) / BR(htt) • D=|RMSSM-RSM|/sexpimental • Decays to SUSY: • H c20c20  (l+l-c10)+(l+l-c10) • Signature: • Four leptons • Large MET CMS Msleptons=250 GeV ATLAS 300 fb-1 CMS

  44. MSSM Higgs: other benchmark points? • ATLAS studies (c. 2003): • preliminary (no syst) • all four special points are well covered at L=30 fb-1 • main workhorse: SM-like VBF with tt-decays • caveat for small aeff: decoupling from tt is compensated by WW enhancement

  45. MSSM Higgs: yet another twist • ATLAS preliminary • VBF Htt, WW • bbH, Htt, mm • tbH± and tH±, H±tn • … • CP-violation in Higgs sector • complex couplings: • mass eigenstates H1, H2, H3 are mixtures of h, H, A • production/decay modes change • new benchmark point CPX (maximum effect) suggested by Carena et al., Phys.Lett B495 (2000) 155 • new parameterization: (MH±,tanb) ATLAS L=30 fb-1 • uncovered holes remain • more studies needed not excluded at LEP!

  46. Summary • Standard Model Higgs: • 0.1 fb-1exclusion limits will start carving into SM Higgs cross section • 0.5 fb-1discoveries become possible if MH~160-170 GeV • 5 fb-1SM Higgs is discovered (or excluded) in full range • forerunner search channels: WW, ZZ, gg • MSSM Higgs: • nearly full (mA, tanb)-plane is covered at L~30 fb-1 • forerunner search channels for h, H/A, H±: gg, tt, tn (assoc’d b/t important) • there is a serious chance to see only a SM-like Higgs…

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