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

17th Sep 2004@Nara, JapanTau04 - 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

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 3

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

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 4

Geneva Airport

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

CERN

Swiss side

France sideJura Mountains

Large Hadron Collider

ATLAS CMS

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 5

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

17th Sep 2004@Nara, JapanTau04 - 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” 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.

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 7

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 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 8

SM Higgs Production at LHCGluon Fusion

Vector Boson Fusion (VBF)

Excluded by LEP

Associated WH, ZH

Associated ttH, bbH

VBF

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 9

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!

17th Sep 2004@Nara, JapanTau04 - 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 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

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 11

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

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 12

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 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 13

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.

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 14

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

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 15

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.

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 16

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

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

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

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 18

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 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 19

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+

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 20

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!!

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 21

END

17th Sep 2004@Nara, JapanTau04 - International workshop on Tau Lepton Physics 22

CMS (Compact Muon Solenoid)

4T solenoid Compact muon spectrometer EM calorimeter PbWO4

Width: 21.5mDiameter: 15mWeight: 12500T