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Discovery Potential of the SM Higgs at the LHC

Discovery Potential of the SM Higgs at the LHC. Junichi Tanaka ICEPP, University of Tokyo. Contents. LHC and ATLAS SM Higgs Production cross section and branching ratio VBF process Key issues Tau identification TauID performance Discovery potential with ~10/fb (~1 year run)

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Discovery Potential of the SM Higgs at the LHC

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  1. Discovery Potential ofthe SM Higgs at the LHC Junichi Tanaka ICEPP, University of Tokyo Tau04 - International workshop on Tau Lepton Physics

  2. Contents • LHC and ATLAS • SM Higgs • Production cross section and branching ratio • VBF process • Key issues • Tau identification • TauID performance • Discovery potential with ~10/fb (~1 year run) • MSSM : Lighter Neutral Higgs • Conclusions CMS, Triggers, SUSY -> Roberto.C’s talk Tau04 - International workshop on Tau Lepton Physics

  3. What is the LHC? 14m x 1232 Proton-Proton (pp) Collider 14TeV • 27km LHC tunnel • Installed in the existing LEP tunnel • 1232 superconducting dipoleswith B = 8.3 T working at 1.9 Kelvin • Two general-purpose pp experimentsATLAS vs CMS Dipole magnet image Tau04 - International workshop on Tau Lepton Physics

  4. Large Hadron Collider LHC tunnel (27km in circumference) （~100m underground） France side Jura Mountains CERN CMS ATLAS Geneva Airport Swiss side Tau04 - International workshop on Tau Lepton Physics

  5. Why is the LHC? High energy High luminosity • Discovery of SM Higgs • ~ the last unobserved particle • Discovery of New Physics Measurement ofSM Higgs properties etc. At the first year 2007~8 (L=10fb-1) LHC is Top & B-factory. LHC can be Higgs & SUSY factory!!! Tau04 - International workshop on Tau Lepton Physics

  6. Time Schedule of LHC • April, 2007 : first beam, commissioning • September, 2007 : 7 months with L=2x1033 cm-2s-1”Low luminosity” run • Physics : L=10fb-1 -> Higgs/SUSY? • 2007~2009 : Low luminosity run • ~2009 : L=1034 cm-2s-1”High luminosity” run ATLAS has started the installation of the detector. Sep. 11th, 2004 ATLAS Tau04 - International workshop on Tau Lepton Physics

  7. ATLAS (A Toroidal LHC ApparatuS) E,P resolution (P ~ 100GeV) : m ~ 2% e, g ~ 1.5% Jets ~ 8% • 40MHz beam crossing • Readout channel = 160M channels • Raw data = 320Mbyte/sec • (1TB/hour) • Inner tracking system : 2T solenoid magnet • Liq. Ar EM calorimeter • Muon spectrometer : air-core troidal magnet Tau04 - International workshop on Tau Lepton Physics

  8. VBF SM Higgs Production at LHC Gluon Fusion Excluded by LEP Vector Boson Fusion (VBF) Associated WH, ZH Associated ttH, bbH Tau04 - International workshop on Tau Lepton Physics

  9. LEPEWWG Summer2003 SM Higgs Decay Branching ratios 114.4 < mH < 193 GeV/c2 @95% C.L. bb, tt, gg, WW, ZZ are important at the lowmass region. Couplings… Observation of Higgs by multi modes Can study Higgs propertiesin detail. Difficult but interesting! Tau04 - International workshop on Tau Lepton Physics

  10. Vector Boson Fusion Process • Characteristics • High Pt jets in forward region • Rapidity gap <- no color flow : no jet activities QCD background can be reduced by these features. • VBF H->tt at low-mass region (mH = ~120GeV) • Large production cross section and branching ratio • Can reconstruct Mtt(=mH) -> Can see a peak -> Discovery channel!! Rapidity gap f h Tau04 - International workshop on Tau Lepton Physics

  11. CMS Hadronic tau decay mode Branching ratio of H->tt : • BR(lep-lep) = ~12% • BR(lep-had) = ~46% “Lep-had” mode plays an important role for the Higgs discovery. factor of ~4 Mtt Distributions of VBF H->tt ＭＨ=120GeV ATLAS (em only) Tau04 - International workshop on Tau Lepton Physics

  12. Key Issues : Strategy for Discovery For “VBF H->tt->lep,had” channel : • More signals • Tau jet identification • High efficiencies of tau jets with high rejection power of QCD jets • Less backgrounds • Missing Et • Better resolution • Make a tail of Z smaller • Make a signal peak shaper ATLAS Tau04 - International workshop on Tau Lepton Physics

  13. Charged tracks : 1 or 3 Photons from p0 Can be measured at InDet. Tau-jet identification Tau-jet = jet originated from hadronic tau decay • We need to identify tau-jets from many QCD-jets. Most/Half of energy are deposited at EM. • Properties of tau-jet • Hadronic decay modes of tau • Narrowness • Shower shape related with decay products (p0,p+-) of t Number of charged tracks Next slide Studying now Tau04 - International workshop on Tau Lepton Physics

  14. Fraction of energy in DR<0.1 (transverse energy) DR<0.4 SET(DR<0.1) DR<0.1 SET(DR<0.4) ~90% of energy are deposited in DR<0.1. -> narrow jet ATLAS, preliminary 20 < Pt < 30 40 < Pt < 50 70 < Pt < 130 Tau-jets QCD-jets These distributions depend on luminosity due to the pile-up. Tau04 - International workshop on Tau Lepton Physics

  15. We achieved eff=50% with Rejection factor > ~100 for Pt > ~40GeV. We misidentify one QCD jet as a tau jet in ~100 QCD jets. ATLAS TDR 1999 TauID Performance No new result. -> studying … Tau04 - International workshop on Tau Lepton Physics

  16. Summary of SM Higgs Studies ATLAS Tau04 - International workshop on Tau Lepton Physics

  17. 10fb-1 ~5s with L=10fb-1 ->Discovery of Higgs within ~ 1 year Discovery potential of SM Higgs Can discover Higgs with L=30fb-1 by >8s (MH>114GeV:LEP limit) MH < 200GeV: - Light case: VBF tt - Heavy case: VBF WW - Can observe Higgs by multi-modes. MH >200GeV: - H->ZZ->4leptonby>20s ATLAS 30fb-1 Tau04 - International workshop on Tau Lepton Physics

  18. Discovery potential of SM Higgs CMS 10fb-1 30fb-1 60fb-1 ~5s with L=10fb-1->Discovery of Higgs within ~ 1 year Tau04 - International workshop on Tau Lepton Physics

  19. MSSM : Lighter Neutral Higgs The lighter neutralhiggs h ~ SM Higgs h mass increases withmA, tanb, top mass,stop mass, stop mixing. bbh coupling is enhanced stronglyat large tanb. + h->mm, tt and bb CMS Tau04 - International workshop on Tau Lepton Physics

  20. Conclusions • SM Higgs can be discovered within 1 year ~ L=10fb-1 at both ATLAS and CMS. • VBF process becomes important for the Higgs discovery in the low-mass region, mH=110~130GeV. • Higher efficiency of tauID with a high purity is necessary to discover Higgs as early as possible. • We need to confirm our tauID using 10fb-1 of real data, Z->tt. • Study of missing Et is also important. • LHC will start at 2007!-> SM Higgs!! and New Physics@TeV!! Tau04 - International workshop on Tau Lepton Physics

  21. END Tau04 - International workshop on Tau Lepton Physics

  22. 4T solenoid Compact muon spectrometer EM calorimeter PbWO4 CMS (Compact Muon Solenoid) Width: 21.5m Diameter: 15m Weight: 12500T Tau04 - International workshop on Tau Lepton Physics

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