1. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics1 Discovery Potential of the SM Higgs at the LHC Junichi Tanaka ICEPP, University of Tokyo

2. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics2 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

3. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics3 What is the LHC? Proton-Proton (pp) Collider 14TeV 27km LHC tunnel Installed in the existing LEP tunnel 1232 superconducting dipoles with B = 8.3 T working at 1.9 Kelvin Two general-purpose pp experiments ATLAS vs CMS 14m x 1232 image Dipole magnet

4. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics4 Geneva Airport LHC tunnel (27km in circumference) （ ~100m underground ） CERN Swiss side France side Jura Mountains Large Hadron Collider ATLAS CMS

5. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics5 Process Event rate at 2×10 33 2007-8 L=10fb -1 Comparison (estimation at 2007 ） tt1.6 Hz10 7 10 4 Tevatron-2 bb: P T >10GeV 200 KHz (HLT 10Hz) 2×10 12 (10 8 inc. di-  ) 10 9 Belle/BaBar Higgs (130GeV) 200/h5×10 5 --------- SUSY (1TeV) 20/h5×10 4 --------- At the first year 2007~8 (L=10fb -1 ) LHC is Top & B-factory. LHC can be Higgs & SUSY factory!!! Why is the LHC? - Discovery of SM Higgs ~ the last unobserved particle - Discovery of New Physics Measurement of SM Higgs properties etc. High energy High luminosity

6. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics6 Time Schedule of LHC April, 2007 : first beam, commissioning September, 2007 : 7 months with L=2x10 33 cm -2 s -1 ”Low luminosity” run Physics : L=10fb -1 -> Higgs/SUSY? 2007~2009 : Low luminosity run ~2009 : L=10 34 cm -2 s -1 ”High luminosity” run Sep. 11th, 2004 ATLAS ATLAS has started the installation of the detector.

7. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics7 ATLAS (A Toroidal LHC ApparatuS) Inner tracking system : 2T solenoid magnet Liq. Ar EM calorimeter Muon spectrometer : air-core troidal magnet E,P resolution (P ~ 100GeV) :  ~ 2% e,  ~ 1.5% Jets ~ 8% 40MHz beam crossing Readout channel = 160M channels Raw data = 320Mbyte/sec (1TB/hour)

8. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics8 SM Higgs Production at LHC Gluon Fusion Vector Boson Fusion (VBF) Excluded by LEP Associated WH, ZH Associated ttH, bbH VBF

9. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics9 SM Higgs Decay bb, , , WW, ZZ are important at the low mass region. Observation of Higgs by multi modes 114.4 < m H < 193 GeV/c 2 @95% C.L. LEPEWWG Summer2003 Branching ratios Can study Higgs properties in detail. Couplings … Difficult but interesting!

10. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics10 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->  at low-mass region (m H = ~120GeV) Large production cross section and branching ratio Can reconstruct M  (=m H ) -> Can see a peak -> Discovery channel!!   Rapidity gap

11. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics11 Branching ratio of H->  : BR(lep-lep) = ~12% BR(lep-had) = ~46% “ Lep-had ” mode plays an important role for the Higgs discovery. Ｍ Ｈ =120GeV M  Distributions of VBF H->  Hadronic tau decay mode factor of ~4 (e  only) CMS ATLAS

12. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics12 Key Issues : Strategy for Discovery For “VBF H->  ->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

13. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics13 Tau-jet identification Tau-jet = jet originated from hadronic tau decay We need to identify tau-jets from many QCD-jets. Properties of tau-jet Hadronic decay modes of tau Narrowness Shower shape related with decay products (  0,  +- ) of  Number of charged tracks Next slide Studying now Most/Half of energy are deposited at EM. Charged tracks : 1 or 3 Photons from  0 Can be measured at InDet.

14. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics14 Fraction of energy in  R<0.1 20 < Pt < 30 40 < Pt < 50 70 < Pt < 130 Tau-jets QCD-jets  R<0.4  R<0.1 ~90% of energy are deposited in  R narrow jet  E T (  R<0.1)  E T (  R<0.4) (transverse energy) These distributions depend on luminosity due to the pile-up. ATLAS, preliminary

15. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics15 TauID Performance No new result. -> studying … ATLAS TDR 1999 We achieved eff=50% with Rejection factor > ~100 for Pt > ~40GeV. We misidentify one QCD jet as a tau jet in ~100 QCD jets.

16. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics16 ProductionDecay Mass region and purpose Gluon Fusion H ->  110-140GeVMass H -> ZZ-> 4 l140-1000GeVDiscovery, Mass, Spin, Coupling H -> WW130-170GeVDiscovery Vector Boson Fusion H ->  110-140GeVDiscovery, Mass, Coupling H -> WW130-200GeVDiscovery, W coupling H ->  110-140GeVDiscovery, Mass H -> bb110-140GeVY b coupling ttH H -> bb110-130GeV Y t coupling H ->  110-130GeV H -> WW130-180GeV WH H -> WW140-170GeVDiscovery, W coupling Summary of SM Higgs Studies ATLAS

17. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics17 Discovery potential of SM Higgs Can discover Higgs with L=30fb -1 by >8  (M H >114GeV:LEP limit) M H < 200GeV: - Light case: VBF  - Heavy case: VBF WW - Can observe Higgs by multi-modes. M H >200GeV: - H->ZZ->4lepton by >20  ATLAS ~5  with L=10fb -1 -> Discovery of Higgs within ~ 1 year 10fb -1 30fb -1

18. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics18 Discovery potential of SM Higgs CMS 10fb -1 30fb -1 60fb -1 ~5  with L=10fb -1 -> Discovery of Higgs within ~ 1 year

19. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics19 MSSM : Lighter Neutral Higgs CMS The lighter neutral higgs h ~ SM Higgs h mass increases with m A, tan , top mass, stop mass, stop mixing. bbh coupling is enhanced strongly at large tan . h-> ,  and bb +

20. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics20 VBF process becomes important for the Higgs discovery in the low-mass region, m H =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- > . Study of missing Et is also important. Conclusions SM Higgs can be discovered within 1 year ~ L=10fb -1 at both ATLAS and CMS. LHC will start at 2007! -> SM Higgs!! and New Physics@TeV!!

21. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics21 END

22. 17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics22 CMS (Compact Muon Solenoid) 4T solenoid Compact muon spectrometer EM calorimeter PbWO 4 Width: 21.5m Diameter: 15m Weight: 12500T