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

17th Sep 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

17th Sep 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

17th Sep 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

17th Sep JapanTau04 - International workshop on Tau Lepton Physics5 Process Event rate at 2× L=10fb -1 Comparison (estimation at 2007 ） tt1.6 Hz 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× SUSY (1TeV) 20/h5× 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

17th Sep 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.

17th Sep 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)

17th Sep 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

17th Sep 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 < m H < 193 GeV/c C.L. LEPEWWG Summer2003 Branching ratios Can study Higgs properties in detail. Couplings … Difficult but interesting!

17th Sep 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

17th Sep 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

17th Sep 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

17th Sep 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.

17th Sep JapanTau04 - International workshop on Tau Lepton Physics14 Fraction of energy in  R< < Pt < < Pt < < 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

17th Sep 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.

17th Sep JapanTau04 - International workshop on Tau Lepton Physics16 ProductionDecay Mass region and purpose Gluon Fusion H ->  GeVMass H -> ZZ-> 4 l GeVDiscovery, Mass, Spin, Coupling H -> WW GeVDiscovery Vector Boson Fusion H ->  GeVDiscovery, Mass, Coupling H -> WW GeVDiscovery, W coupling H ->  GeVDiscovery, Mass H -> bb GeVY b coupling ttH H -> bb GeV Y t coupling H ->  GeV H -> WW GeV WH H -> WW GeVDiscovery, W coupling Summary of SM Higgs Studies ATLAS

17th Sep 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

17th Sep 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

17th Sep 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 +

17th Sep 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

17th Sep JapanTau04 - International workshop on Tau Lepton Physics21 END

17th Sep 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