Discovery Potential of the SM Higgs at the LHC

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 1

Discovery Potential ofthe SM Higgs at the LHC

Junichi TanakaICEPP, 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) MSSM : Lighter Neutral Higgs Conclusions

CMS, Triggers, SUSY -> Roberto.C’s talk


What is the LHC?

Proton-Proton (pp) Collider 14TeV

• 27km LHC tunnel• Installed in the existing LEP tunne

l

• 1232 superconducting dipoleswith B = 8.3 T working at 1.9 Kelvin

• Two general-purpose pp experimentsATLAS vs CMS

14m x 1232

image

Dipole magnet


Geneva Airport

LHC tunnel (27km in circumference)（ ~100m underground）

CERN

Swiss side

France sideJura Mountains

Large Hadron Collider

ATLAS CMS


ProcessEvent rate at 2×1033

2007-8 L=10fb-1

Comparison(estimation at

2007）tt 1.6 Hz 107 104 Tevatron-2

bb: PT>10GeV200 KHz

(HLT 10Hz)2×1012

(108 inc. di-)109 Belle/BaBar

Higgs (130GeV)

200/h 5×105 ---------

SUSY (1TeV) 20/h 5×104 ---------

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 ofSM Higgs properties etc.

High energy High luminosity


Time Schedule of LHC• April, 2007 : first beam, commissioning• September, 2007 : 7 months with L=2x1033 cm-2s-1 　　” Low luminosity” r

un

　　　　 Physics : L=10fb-1 -> Higgs/SUSY?

• 2007~2009 : Low luminosity run• ~2009 : L=1034 cm-2s-1 ”High luminosity” run

Sep. 11th, 2004ATLAS

ATLAS has started theinstallation of the detector.


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)


SM Higgs Production at LHCGluon Fusion

Vector Boson Fusion (VBF)

Excluded by LEP

Associated WH, ZH

Associated ttH, bbH

VBF


SM Higgs Decay

bb, , , WW, ZZare important at the lowmass region.

Observation of Higgs by multi modes

114.4 < mH < 193 GeV/c2 @95% C.L.

LEPEWWG Summer2003

Branching ratios

Can study Higgs properties in detail.

Couplings…

Difficult but interesting!


Vector Boson Fusion Process

Characteristics High Pt jets in forward region Rapidity gap <- no color flow : no jet activitiesQCD background can be reduced by these features.

VBF H-> at low-mass region (mH = ~120GeV) Large production cross section and branching ratio Can reconstruct M(=mH) -> Can see a peak-> Discovery channel!!

Rapidity gap


Branching ratio of H-> :• BR(lep-lep) = ~12%• BR(lep-had) = ~46%“Lep-had” mode plays an important role for the Higgs discovery.

ＭＨ =120GeV

h

4M Distributions of VBF H->

Hadronic tau decay mode

factor of ~4

(e only)

CMS

ATLAS


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


Tau-jet identificationTau-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 3Photons from 0

Can be measured at InDet.


Fraction of energy in R<0.1

20 < Pt < 30

40 < Pt < 5070 < Pt < 130Tau-jetsQCD-jets

R<0.4

R<0.1 ~90% of energy are depositedin R<0.1. -> narrow jet

ET(R<0.1)ET(R<0.4)

(transverse energy)

These distributions depend on luminosity due to the pile-up.

ATLAS, preliminary


TauID Performance

No new result.-> studying …

ATLAS TDR 1999

We achieved eff=50% withRejection factor > ~100 forPt > ~40GeV.

We misidentify one QCD jetas a tau jet in ~100 QCD jets.


Production Decay Mass region and purpose

Gluon FusionH -> 110-140GeV Mass

H -> ZZ-> 4 l 140-1000GeV Discovery, Mass, Spin, Coupling

H -> WW 130-170GeV Discovery

Vector BosonFusion

H -> 110-140GeV Discovery, Mass, Coupling

H -> WW 130-200GeV Discovery, W coupling

H -> 110-140GeV Discovery, Mass

H -> bb 110-140GeV Yb coupling

ttH

H -> bb 110-130GeV

Yt couplingH -> 110-130GeV

H -> WW 130-180GeV

WH H -> WW 140-170GeV Discovery, W coupling

Summary of SM Higgs StudiesATLAS


Discovery potential of SM Higgs

Can discover Higgs withL=30fb-1 by >8(MH>114GeV:LEP limit)

MH < 200GeV:- Light case: VBF - Heavy case: VBF WW- Can observe Higgs

by multi-modes.

MH >200GeV:- H->ZZ->4lepton by >20

ATLAS

~5 with L=10fb-1

　 ->　Discovery of Higgs within ~ 1 year

10fb-1

30fb-1


Discovery potential of SM Higgs

CMS

10fb-1

30fb-1

60fb-1

~5 with L=10fb-1 ->　 Discovery of Higgs within ~ 1 year


MSSM : Lighter Neutral Higgs

CMS

The lighter neutralhiggs h ~ SM Higgs

h mass increases withmA, tan, top mass,stop mass, stop mixing.

bbh coupling is enhanced stronglyat large tan.

h->, and bb+


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->

. 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!!


END


CMS (Compact Muon Solenoid)

4T solenoid Compact muon spectrometer EM calorimeter PbWO4

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Discovery Potential of the SM Higgs at the LHC

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