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ATLAS Potential at High Luminosity

ATLAS Potential at High Luminosity. Bing Zhou (for ATLAS collaboration). LHC. SM / MSSM Higgs discovery Precision Higgs boson parameter measurements If no Higgs, longitudinal gauge boson scattering at high mass region The mass reach for extra-dimension models

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ATLAS Potential at High Luminosity

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  1. ATLAS Potential at High Luminosity Bing Zhou (for ATLAS collaboration) LHC • SM / MSSM Higgs discovery • Precision Higgs boson parameter measurements • If no Higgs, longitudinal gauge boson scattering at high mass region • The mass reach for extra-dimension models • Search for technihadron resonancein TeV scale • Precision gauge coupling measurements • Initial luminosity: 2x1033 cm-2s-1 Eb =7 TeV • Design luminosity (1034 cm-2s-1) should be reached after 2-3 years of operation • Phase 0 upgrade: luminosity: 2.3x1034 cm-2s-1Eb =7.54 TeV • Phase 1 upgrade: 9x1034 cm-2s-1Eb =7.54 TeV • Phase 2 upgrade: 9x1034 cm-2s-1Eb =14 TeV Super LHC Physics reach -- ATLAS examples Physics

  2. Length: ~44 m Radius: ~12 m Weight: ~ 7000 t El. Channels: ~10 8 Cables: ~3000 km The ATLAS Detector Precision Muon Spectrometer Fast response for trigger Good p resolution (e.g., A/Z’  , H -> 4) Inner Detector Good impact parameter res. (e.g., H  bb) EM Calorimeters excellent electron/photon identification Good E resolution (e.g., Hgg) Hadron Calorimeters Good jet and ET miss performance (e.g., H )

  3. Higgs Production Mechanisam @ LHC 4 production mechanisms key to measure H-boson parameters

  4. Higgs Discovery Channels at LHC • Dominant BR for mH<2mZ: •  (H  bb)  20 pb; •  (bb)  500 b • for m(H) = 120 GeV • no hope to trigger or extract fully hadronic final states • look for final states with ,  ( = e, ) m(H) > 2 mZ : H  ZZ  4 qqH  ZZ    *qqH  ZZ   jj * qqH  WW jj **for mH > 300 GeV forward jet tag Low mass region: m(H) < 2 mZ : H   : small BR, but best resolution H  bb : good BR, poor resolution  ttH, WH H  ZZ*  4 H  WW*   or jj : via VBF H   : via VBF

  5. Light Higgs Search: H -> ZZ* -> 4m ATLAS / 10 fb-1 MH = 300 GeV required lumi. for discovery 100 fb–1 No K-factors 100 fb–1

  6. Light Higgs Search: gg, ttH channels Significance: 2.8 to 4.3 for 100 fb-1 Signal significance (5) : mH < 120 GeV needs 100 fb–1

  7. n l W p p H W Light Higgs Search: H  WW*   mT = 2pTETmiss(1-cosf) • Two isolated leptons • Two forward tag jets • Central jet veto: pT<20 GeV • lepton angular correlation n l Results for 5 fb–1, 5% background syst.

  8. SM Higgs Discovery Potential ATLAS All channels together • LHC can probe entire set of ”allowed” Higgs mass values (100 GeV – 1 TeV) • at least 2 channels for most of range (No K-factors) Without WBF at low mass Significant boost from WBF at low mass 30 fb-1 30 fb-1

  9. Search for MSSM Higgs(es) Complex analyses; 5 Higgses: h0, H0, A0, H • At tree level, all masses and couplings depend on: MA and tanb Large variety of observation modes • if SUSY particles heavy • SM-like:h gg, bb H  4l • MSSM-specific:A/H mm, tt, tt H  hh A  Zh H tn • if SUSY particles accessible: • H/A  c20 c20 c10 c10 4l + missing Energy • h produced in cascade decays (e.g.c20 hc10)

  10. MSSM Higgs Discovery Potential • Plane fully coveredwith 30 fb-1 • 2 or more Higgses observable in large fraction of plane 300 fb-1 • Precision ~ 7-20%

  11. Measurement of Higgs Properties At High Luminosities Process investigated in ATLAS

  12. Measurement of Higgs Properties SM Mass measurement • Limited by absolute energy scale • 0.1% for l/g (Z  ll calibration) • 1% for jets • Resolutions: • For gg & 4l ≈ 1.5 GeV/c2 • For bb ≈ 15 GeV/c2 • At large masses: decreasing precision due to large GH 300 fb-1 MSSM • h as in SM case • H/A: 0.1 - 0.5% in modes gg, 4l, mm • 1 - 2% in modes bb, bbgg (hh), bbll (Zh)

  13. Measurement of Branching Ratios • Measurement of relative branching ratios • Fitting Br(H->XX) (assume Higgs production works as in SM)

  14. Measurement of Higgs Couplings Measurement of relative couplings Measurement of couplings

  15. Higgs Self-couplings Cross section of the Higgs pair production at LHC Need Super LHC to measure Higgs self-interaction couplings: For 6000 fb-1(SLHC) Dl ~ 19% for 170 GeV MH

  16. Rare Higgs Decay Modes at SLHC Examples mmg (eeg) Cross section ~ 2.5 fb (MH = 100-160 GeV) H Z g With 600 fb-1 , signal significance ~ 3.5 s additional H-Z coupling measurement With 6000 fb-1 , signal significance ~ 11s H mm In SM, this decay channel has 10-4 Br With 6000 fb-1, the expected statistical accuracy on the measurement of the production of cross-section times Br is given below :

  17. Strongly-Coupled Vector Boson System No light Higgs boson? Study Longitudinal gauge boson scattering in high energy regime (the L-component which provides mass to these bosons). WL ZL l n l l WL ZL S / B = 6.6/2.2 ~ 10

  18. ZL ZL Scalar Resonance WL WL -> ZL ZL-> 4 leptons ZL ZL -> ZL ZL-> 4 leptons V V V V 3000 fb-1 (14 TeV) V V X X V V

  19. Beyond SM: Extra Dimension Models Extra dimension models aim at incorporating gravity in the scheme Of unification of gauge interactions and explain the hierarchy LHC experiments will be able to probe some models:

  20. Xdim: Direct Graviton Production Signal Jet + missing Et Signals Events for high luminosity 100 fb-1, for Etjet > 1 TeV 100 fb-1 Significance

  21. Xdim: Virtual Graviton Exchange Experimental signature: large enhancement in di-lepton mass distribution (similarly for di-photons mass distribution) Sensitivity in ATLAS (combine 2 channels) d 2 3 4 5 lumi Msmax (TeV) 7.0 6.3 5.7 5.4 10 fb-1 Msmax (TeV) 8.1 7.9 7.4 7.0 100 fb-1

  22. Charge confusion prob. of The ATLAS muon system

  23. Extra Dimensions of ~ TeV-1 Size (100 fb-1) Signal: di-lepton resonance g /Z Z/M2 (100 fb-1) Z’ G* Resonance observable Up to ~ 6 TeV with 100 fb-1

  24. Narrow Graviton Resonance: Spin of G ATLAS can distinguish spin 2 vs. 1 up to ~ 2 TeV

  25. Strong Symmetry BreakingTechnicolor No fundamental scalar Higgs (it is a new strong force bounded state) Technicolor predicts existence of technihadron resonance (pT, rT, . . .) Technicolor channels investigated Main background for signals: Z + jets (qq->gZ, gg-> qZ, qq->ZZ) tt, WZ continuum production

  26. Signal of Technicolor Example rT -> WZ -> l n l l

  27. Triple Gauge Boson Couplings Open window to electroweak Symmetry breaking mechanism LHC: orders of magnitude Improvement over LEP/Tevatron (particularly, l type couplings) Expected 95% C.L. constrains contours (outer-> inside): (14TeV, 100fb-1), (28TeV, 100fb-1), (14TeV, 1000fb-1), (28TeV, 1000fb-1)

  28. Quartic Gauge Boson Couplings 100fb-1 6000fb-1 100fb-1 6000fb-1

  29. Summary • SM / MSSM Higgs could be discovered with ~ 10 – 30 fb-1 • Precise measurements of Higgs parameters with 600 fb-1: masses to 0.1 – 1%, width to ~ 5-30%, couplings to 10-30% • Rare Higgs decay modes and Higgs self-interactions can be observed with 600-6000 fb-1 • If no Higgs, resonance and non-resonance scattering gauge boson pairs at high mass could be fully explored with signal significance ~ 10 for 3000 fb-1. • The mass reach for extra-dimension models, new gauge bosons will be extended up to O(10 TeV) at high luminosities. • Measurements of triple & quartic gauge boson couplings can be measured with very high precisions • Many other more interesting new topics to be explored… • More importantly , we are to exploring UNKNOWN at LHC!

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