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Physics @ LHC (Physics @ TeV)

Physics @ LHC (Physics @ TeV). Status of LHC/ATLAS/CMS and Physics explored at LHC. Fundamentalist of High Energy Physics (U. Tokyo). [3] Origin of Mass (Higgs). SSB of Higgs Potential gives mass to Gauge boson W/Z: (Freedom of ξ) Motion in η is corresponding to Higgs boson.

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Physics @ LHC (Physics @ TeV)

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  1. Physics @ LHC (Physics @ TeV) Status of LHC/ATLAS/CMS and Physics explored at LHC Fundamentalist of High Energy Physics (U. Tokyo)

  2. [3] Origin of Mass (Higgs) SSB of Higgs Potential gives mass to Gauge boson W/Z: (Freedom of ξ) Motion in η is corresponding to Higgs boson Simulated H→γγ events Higgs boson will be observed at LHC like this event (simulation)

  3. [3-1] Production processes of SM Higgs at LHC 4 processes Gluon Fusion Vector Boson Fusion Associate production with W/Z GF & VBF are important for discovery: Cross-section of ttH/bbH is small, but give the direct information of Yukawa yt/yb. Associate production with t/b

  4. Detector Central f Vector Boson Fusion (1998Zeppenfeld et al.) VBF has an excellent potential because of : η (1) Scattered “high Pt” jets are observed in the forward regions. Pt 〜 Mw (2) There is rapidity gap between two jets because there is no color exchange. Only the products from Higgs are observed in the central region. These are very promising signatures in order to suppress the background. QCD(color exchange) VBF Number of jets η

  5. Precision measurements of the SM at LEP suggests M(H)=115-200GeV(95%CL) [3-2] Decay Branching Fraction In such a light region, there are 5 important decay modes. H→ bb,tautau,γγ (M(H)<140GeV) H→ ZZ(*),WW(*) (M(H)>130GeV) H → γγBr is small of about 10-3, Butpromising mode due to good resolution of γ

  6. [3-3A] H→ γγin GF and VBF (small Br, but excellent Mγγ） H+0j huge BG. S/N ~1% qq_bar→ γγis dominante BG is High but also signal stat. is high Xsection (fb/GeV) ATLAS preliminary Two leading processes contribute to three different event topologies: S/N and shape of BG are different in 3 class. Discovery potential of them are similar, and we have good redundancy. Xsection (fb/GeV) H+1j γ-ID and resolution are essential : BG can be estimated with the side band. Mgg(GeV) H+2j ATLAS preliminary Xsection (fb/GeV) Mgg(GeV) Good S/N and flat BG but Stat. limited H→γγ indicates that spin of Higgs is 0 (or 2).  scalar Mgg(GeV)

  7. [3-3B] H→ZZ(*)→　４leptons Resolution and identifications of leptons are excellent. Invariant mass distributions of 4 leptons are shown with BG contributions. Irreducible BG is qq_bar → ZZ* → 4l (continuous distribution) Reducible BGs are tt & Zbb (lepton comes from semileptonic decay of B B contamination can be suppressed by isolation of track + anti-impact parameter Track quality is essential for this mode ) CMS Full M(H)=200GeV M(H)=140GeV ZZ*→ 4l has excellent discovery potential except for M(H)<130GeV and M(H)=170GeV (Branching is small): We can determine also CP, Spin of Higgs using this channel.

  8. This mode is direct evidence of Higgs-fermion coupling (Yukawa) Origin of fermion mass Tau decay includes neutrino, but Momenta of ν’s can be calculated using mET information in the collinear limit.  Tau can be reconstructed !!!! [3-3C] ＶＢＦ　H→ττ ATLAS Fast CMS Full Resolution of mET is about 10GeV Mtautau has sharp peak (sigma 〜 10GeV) Dominant Background process is Z(→tautau)+Njets. Peak appears at 91GeV.  Resolution and tail of mET distribution are essential for this channel

  9. Higgs Spin0 W- W+ e+ e- [3-3D] VBF Ｈ→　WW Leptonic decays of W lead to the event topology of Dilepton+mET Leptons are emitted in the same direction MＨ=160GeV ATLAS CMS Full Clear Jacobian Peak is observed: tt → bb lνlν is main BG: Leptons are back-to-back in tt. Φ between di-lepton (Rad)

  10. [3-4] Discovery Potential of the SM Higgs LO calculation NLO calculation Similar Discovery potentials are obtained at both ATLAS and CMS (Notice LO calculation vs NLO) VBF γγ+ exclusive 1,2 jets analyses will gain significance in low mass regions H->γγ, tautau covers the region < 130GeV, WW,ZZ > 130GeV 5sigma discovery is possible with L=10fb-1for both ATLAS and CMS Different technologies are essential for various modes: (Safe and redundant)

  11. Needed Ldt (fb-1) per experiment 10 1 ATLAS + CMS preliminary 10-1 mH (GeV) Let’s combine ATLAS+CMS performance  1 fb-1 for 98% C.L. exclusion  5 fb-1 for 5 discovery over full allowed mass range --- 98% C.L. exclusion • 5σ discoveryis possible within • 2008(>130GeV) or • early of 2009(<130GeV) •  measurements of mass, coupling, spin • 98%CL exclusion (2008) • No Higgs model? invisible decay? • No resonance? criticaltest can be performed for “origin of mass”

  12. [3-5] Measurements of Mass & coupling (L=300fb-1) Relative coupling (Normalized to g(WH)) • Yｔ, Yτ 10-15% • Yb 30-40% • Gz、5-10% Mass can be measured with accuracy of 0.1% if M(H)<400GeV. We can show couplings are proportional to their masses

  13. Accuracy of “absolute measurements” of the couplings. We assume the SM branching fractions except for the leading five processes: Br(H->tautau,tt,bb,ZZ and WW) Within this assumption, Couplings of yt、yτ、yb, gZZH and gWWH can be calculated. Accuracy: yt、yτgZZH and gWWH 20% yb 50%

  14. Higgs Self-couplings In order to determine the shape of Higgs potential, Slope of potential is correspond to Self-coupling σ×Br is small Need very High Luminosity ー＞SLHC For 6000 fb-1(SLHC) Dl ~ 19% for 170 GeV MH

  15. ＳＭ Higgsの研究で有効なチャンネルの纏め

  16. Diphoton background is now computed at NLO(Binoth et al, Eur.Phys.J.C16(2000)311, Bern,Dixon,Schmidt hep-ph/0206194, C.Balasz et al, Phys.Lett.B489(2000)157

  17. 1-6 ＭSSM Higgsの発見能力 軽いhはSM解析、 ほぼそのまま • tanβが大きいとbbH/Aの • 結合が大きくなる。 • H/A→ττ・μμ・(bb) • tanβ>10で　gb->tH-でcharged Higgs が観測可能 →MSSM Higgsも必ず L=30fb-1のrunで発見可能 ここら辺以外は１年でOK (t →H+b がcover) この緑の部分は、HＳＭに似た性質のhが観測されるだけ。（SUSY decay )

  18. H/A生成 tanβ ←tanβ２で数が 増えるので見える gg→bbH/A→ττ、μμ、（bb） ←μのyukawa*tanβ 第２世代のYukawaを見るチャンス 10

  19. H/A生成 tanβ gg→bbH/A→ττ、μμ、bb 10 tanβを測定する重要なチャネル 軽いhがLEP見えない->大きなtanβ

  20. Ｈ＋− (t,b) Br=90% (τν) 10% の時suppress

  21. [6] Introduction and Conclusion: Most important/urgent topics in Particle Physics are: Understanding of “the origin of mass” (EW symmetry breaking) SSB of Higgs field is most promising scenario, but should be examined directly: & determine the potential: (2) Beyond the Standard Model Supersymmetry is most promising, Large Extra Dimension, unexpected scenario… are also exciting. These are main purpose of LHC project: and LHC will give the clear solutions

  22. 2008 !! Appendix: Mt can be measured with accuracy of 0.9GeV, Mw will be 15MeV(Very difficult task. Z’ or high mass gauge boson 5TeV, Littele Higgs heavy top 1TeV

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