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Higgs Physics Higgs Physics with ATLAS with ATLAS Markus Schumacher, Bonn University Seminar über Teilchenphysik, Wuppertal, November 10th 2005

Higgs Physics with ATLAS

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Higgs Physics with ATLAS. Markus Schumacher, Bonn University. Seminar über Teilchenphysik, Wuppertal, November 10th 2005. Outline. the Higgs Mechanism and SM Higgs phenomenology at LHC discovery potential for SM Higgs boson investigation of the Higgs boson profile - PowerPoint PPT Presentation

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Page 1: Higgs Physics with ATLAS

Higgs PhysicsHiggs Physics

with ATLASwith ATLAS Markus Schumacher, Bonn University

Seminar über Teilchenphysik, Wuppertal, November 10th 2005

Page 2: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 2

Outline

the Higgs Mechanism and SM Higgs phenomenology at LHC

discovery potential for SM Higgs boson

investigation of the Higgs boson profile

phenomenology of SUSY Higgs bosons

discovery potential for MSSM Higgs bosons

discriminating the SM from extended Higgs sectors

conclusion and outlook

Page 3: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 3

The Higgs Mechanism in the Nut Shell

consistent description of nature seems to be based on gauge symmetry

SU(2)LxU(1) gauge symmetry no masses for W and Z and fermions „ad hoc“ mass terms spoil

The problem:

The „standard“ solution:

new doublet of complex scalar fields

with appropiately choosen potential V

vacuum spontaneously breaks gauge symmetry

one new particle: the Higgs boson H

= v + H

• renormalisibilty no precise calculation of observables

• high energy behaviour WLWL scattering violates unitarity at ECM~1.2 TeV

Page 4: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 4

Mass generation and Higgs couplings: = v + H

effective mass = friction of particles

with omnipresent „Äther“

v =247 GeVx

fermion

gf

mf ~ gf v Yukawa coupling

MV ~ g v gauge coupling

x x

W/Z boson

g gauge

Interaction of particles with v=247 GeV

Fermions gf ~ mf / v

W/Z Bosons: gV ~ 2 MV / v

Interaction of particles with Higgs H

fermion

gf

x

W/Z boson

g gauge

Higgs

Higgs v

2

2VVH coupling ~ vev

only present after EWSB breaking !!!

1 unknown parameter in SM: the mass of the Higgs boson

Page 5: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 5

50 100 200 100010-3

10-2

10-1

100

bb cc tt gg WW ZZ

Bra

nchi

ng r

atio (Higgs

)

mH (GeV)

bb

WW

ZZ

tt

ccgg

Higgs Boson Decays in SM

for M<135 GeV: H bb, dominant

for M>135 GeV: H WW, ZZ dominant

tiny: H also important

HDECAY: Djouadi, Spira et al.

Page 6: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 6

Status of SM Higgs Searches I: LEP

MH < 186 GeV

at 95% CL ,mtop=172 GeV

(MH<216 GeV for mtop=175 GeV)

MH<114.4 GeVexcluded at 95% CL

Direct search:

Electroweak fit:

Page 7: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 7

Status of SM Higgs Searches II: TEVATRON

Expected sensitivity:

95% CL exclusion up to 130 GeV with 4fb-1 per experiment

3 sigma evidence up to 130 GeV with 8fb-1 per experiment

Current sensitivity::

Cross section limits at level of

~ 10 x SM cross section

Page 8: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 8

1) mass

2) quantum numbers:

spin and CP

3) BRs, total width, couplings

4) self coupling at SLHC

Higgs Physics at LHC

discovery of 1 neutral scalar Higgs boson

(determination of mass, spin, CP)

discrimination between SM and extended Higgs sectors

1) > 1 neutral Higgs boson

2) charged Higgs boson

3) exotic decay modes

e.g. H invisible

4) … … …

direct observation of

additional Higgs bosons

determination of Higgs profile:

deviations from SM prediction

Page 9: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 9

LHC and ATLAS

LHC: proton proton collisions at ECM = 14 TEV, start in 2007

- low luminosity running: 1(2)x1033 /(cm2 s) 10(20) fb-1/year- high luminosity running: 1034/(cm2 s) 100 fb-1/year

A Toroidal LHC Aparatus •design optimised for low mass Higgs boson discovery:

• H2 photons, HZZ 4 leptons

anticipated M/MH ~ 1 % em.-calorimetry, spectrometer

• ttH, Hbb

b=60(50)% Rc>10 Rudsg>100 Si tracking detectors• Htau tau, WWll, VBF prod. missing E. resolution, hermiticity, forward jets calorimetry to = 5

MC studies with fast simulation of ATLAS detector key performance numbers from full sim.: b/tau/jet/el.// identification, isolation criteria, jet veto, mass resolutions, trigger efficiencies, …

Page 10: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 10

Production of the SM Higgs Boson at LHC

Page 11: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 11

QCD corrections and Knowledge of Cross Sections

K = NNLO/LO~2

= 15% from scale variations

error from PDF uncertainty ~10%

Caveat: scale variations may underestimate the uncertainties!

ttH: K ~ 1.2 ~ 15% WH/ZH: K~1.3 to1.4 ~7%

VBF: K ~ 1.1 ~ 4% + uncertainties from PDF (5 to 15%)

but: rarely MC at NLO avaiable (except gluon gluon fusion)

background: NLO calculations often not avaiable

need background estimate from data

ATLAS policy: use K=1 for signal

e.g.: Gluon Gluon Fusion

Harlander et al.

Page 12: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 12

Cross sections for Background Processes

Higgs 150 GeV: S/B <= 10-10

overwhelming background

trigger: 10-7 reduction

on leptons, photons, missing E

p pqq

q

p pqq

qq

H

WW

l

l

Background: mainly QCD driven

Signal: often electroweak interaction

photons, leptons, …

q

Page 13: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 13

Discovery Potential for light SM Higgs boson

discovery channels

GGF: H GGF: H ZZ 4l+-

GGF: HWW2(l)

ttH: H bb

VBF: H

VBF: H WW For MH>300 GeV also:

VBF: H ZZ ll

VBF: WW lqq

no fully hadronic final states: eg. GGF, VBF: Hbb

Higgs Boson mass reconstruction possible?

background controlable (S/B), estimate from data possible?

excl

ud

ed b

y L

EP

For MH>330 GeV also:

VBF: H ZZ ll

VBF: WW lqq

excl

ud

ed b

y L

EP

since 2000

Page 14: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 14

H 2 Photons

ATLAS

signature: two high Pt background: irreducible pp +x

reducible ppj, jj, …

exp issues (mainly for ECAL):

, l+-, 0 separation (jet fake rate 10-4)

- energy scale, angular resolution

- conversions/dead material

mass resolution M: ~1%

precise background estimate

from sidebands (O(0.1%))

S/BG ~ 1/20

ATLAS 100fb-1

Page 15: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 15

Gluon Fusion: H ZZ(*)4 Leptons

signature:

4 high pt isolated leptons

1(2) dilepton mass ~ MZ

irreducible BG: ZZ

mass reconstruction

reducible BG:

tt, Zbb 4 leptons

rejection via

lepton isolation and b-vetoATLAS TDR

good mass resolution M: ~1%

small and flat background easy estimate from data

Page 16: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 16

Gluon Fusion: H WW l l

ATLAS

M=170GeV

L=30fb-1

signature:

- 2 high pt leptons + large missing ET

- lepton spin corrleations

- no mass peak transverse mass

transverse mass

BG: WW, WZ, tt

lepton iso., missing E resolution

jet (b-jet) veto against tt

BG estimate in data from ll

NLO effect on spin corr.

ggWW contribution signal like

Dührssen, prel.

ll

Page 17: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 17

ttH with Hbb

mass resolution M: ~ 15%

50% correct bb pairings

very difficult background estimate from

data with exp. uncertainty ~ O(10%)

normalisation from side band

shape from „re-tagged“ ttjj sample

reducible BG: tt+jets, W+jets b-tagging

irreducible BG: ttbb reconstruct mass peak

exp. issue: full reconstruction of ttH final state combinatorics !!! need good b-tagging + jet / missing energy performance

S/BG ~ 1/6

30 fb-1

only channel to see Hbb

ATLAS

signature: 1 lepton, missing energy

6 jets of which 4 b-tagged

Page 18: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 18

Vector Boson Fusion: ppqqH

Jet

Jet

signature:

-2 forward jets with

large rapidity gap

- only Higgs decay products in central part of detector

Forward tagging jets

Higgs Decay

Page 19: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 19

Vector Boson Fusion: ppqqH

2 forward tagging jets with rapidity gap:

pT>20GeV

forward jet reconstruction

ATLASHigh Lumi

Low Lumi

jet-veto fake rate due to pile up

ATLAS

theory questions:

jet distributions at NLO?

esp. direction of 3rd jet?

efficieny of central jet veto?need NLO MC generator

for signal and BG

experimental issues:

Page 20: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 20

signature: tagging jets +

- 2 high pt leptons + large missing ET

- lepton spin corrleations (spin10)

- no mass peak transverse mass

Weak Boson Fusion: HWWll (lqq)

tt, Wt, WWjj, ...

backgrounds:

HWWeATLAS

10 fb-1MH=160 GeV

S/BG ~ 3.5/1 BG uncertainty ~ 10 %

shape from MC

normalisation from side bands in

MT and ll

central jet vetob-veto

Page 21: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 21

ATLAS

He

Vector Boson Fusion: H tau tau ll 4 (l had 3 )

mass resolution ~ 10%

determined by missing E. resolution BG uncertainty ~ 5 to 10%

for MH > 125 GeV: flat sideband

for MH < 125 normalisation from Z peak

30 fb-1

MH=120 GeV

signature: tagging jets +

- 2 high pt leptons + large missing ET

- mass reconstruction despite 4 in collinear approximation

backgrounds: Zjj, tt

S/BG ~ 1 to 2 / 1

central jet veto

reconstructionof m

Page 22: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 22

Vector Boson Fusion, Hestimate of BG shape from dataIdea: jjZandjjZ

look almost the same esp. in calos

same missing energy

only momenta different

Method: select Z events

randomise momenta

apply „normal“ mass reco.

PTmiss,final (GeV) M (GeV)

promising prel. results from ongoing diploma thesis in BN (M. Schmitz)

Page 23: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 23

SM discovery potential depending on int. luminosity

excl

ud

ed b

y L

EP

discovery from LEP exclusion until 1 TeV

from combination of search channels with 15 fb-1 of well understood data

with individual search channels with 30 fb-1 of well understood data

Page 24: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 24

Investigation of Higgs boson profile

1) Mass determines completly SM phenomenology

2) Spin and CP QN Is it a CP even scalar boson?

3) Couplings Is it responsible for mass generation?

test SM prediction with best accuracy

look for deviations hint towards new physics

Page 25: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 25

Measurement of Higgs Boson Mass

1fb300L

ATLAS

M/M: 0.1% to 1%

Uncertainties considered:

“Indirect” from Likelihood fit to transverse mass spectrum: HWWllWHWWWlll

Direct from mass peak: HHbb HZZ4l

VBF with H or WW

not studied yet !

i) statistical

ii) absolute energy scale

0.1 (0.02) % for l,,1% for jets

iii) 5% on BG + signal for HWW

Page 26: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 26

sensitivity through spin correlations of Higgs decay products

one possibility HZZ4 leptons

))(cos()(sin)( 22 1TLG

TL

TLR

Spin and CP Quantum Numbers: 0 even in SM

: angle btw. decay planes

:angle btw. leptons and Z

in Z rest frame

(Gottfried Jackson angle)

Higgs rest frame

observation of Hor ggH rules out Spin=1 (Young theorem)

L (T) ratio of longitudinal (tranverse) polarised Z bosons

100 fb-1

Page 27: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 27

Spin and CP Quantum Numbers: discrimination power

alternative methods:

decay: H via spin correlations

production: i) ttH angle between t,t,H ii) VBF btw. tagging jets

discrimination dominated by for masses > 250 GeV

seperation power > 2 for all

spin, CP hypothesis and MH>200 GeV

currently under study:

- NLO effects

- verification with full sim. + all BGs

- lower masses HZZ*

Page 28: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 28

Determination of Higgs boson couplings

Loop induced effective couplings:(sensitive to new physics)

Photon: g = gW “+“ gt “+“…

Gluon: g = gt “+“ gb “+“…

Hx

x

Born level couplings:

Fermions gf = mf / v

W/Z Bosons: gV = 2 MV / v2

couplings in production Hx= const x Hx and decay BR(Hyy) = Hy / tot experiment: rate = Nsig+NBG Nsig= L x efficiency x Hx x BR

need to know: luminosity, efficiency, background

Hx x BR ~ HX Hy

tot

prod decay

partial width: Hz ~ gHz2

tasks: - disentangle contribution from production and decay

- determine tot

Page 29: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 29

ratios of BRs = ratios of = ratios of g, if only Born level couplings

W

totW

totWW

)BR(HWW)BR(H

VBF

VBF

→e.g.

WWHZH,

WWHWH,

WWHttH,

WWHVBF,

WWHGF,

BR)(

BR)(

BR)(

BR)(

BR)(

W

b

WWW

Z

9 fit parameters:

all rates can

be expressed

by those 9

parameters

H WW chosen as reference as best measured for MH>120 GeV

For 30fb-1 worse by factor 1.5 to 2

13 analysis used

Ratio of Partial Widths

including various exp. and theo. errors

Page 30: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 30

Total Decay Width H

for MH>200 GeV, tot>1GeV

measurement from peak width in ZZ4 l

upper limit needs input from theory:

mild assumption: gV<gVSM

valid in models with only Higgs doublets and singlets

rate(VBF, HWW) ~ V2 / tot < (V

2 in SM)/ tot

tot< rate/(V2 in SM)

lower limit from observable rates:

tot > W+Z+t+g+....

for MH<200 GeV, tot<< mass resolution

no direct determination

have to use indirect constraints on tot

Page 31: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 31

Absolute couplings with gV < gVSM constraint

coupling to W, Z, , b, t

g/g = ½ g2)/g2

inv for undetactable decays

e.g. c, gluons,newphoton (new), gluon (new):

non SM contribution to loops

g/g = ½ g2)/g2

Page 32: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 32

MH2 = 2 =MPlanck

Motivation for Supersymmetry from Higgs Sector

Higgs problem in SM: large corrections to the mass of the Higgs-Boson

2

“solves” hierarchy problem: why v = 246 GeV << MPl=1019GeV ?

MH2 = (MSM-MSUSY)

2 2

W W+ HH

natural value ~ MPl electroweak fit MH~O(100GeV)

SUSY solution: - partner with spin difference by ½ cancel divergence exactly if same M- SUSY broken in nature, but hierarchy still fine if MSUSY~1 TeV

H H

-

SUSY breaking in MSSM: parametrised by 105 additional parameters too many constrained MSSM with 5 (6) additional parameters

Page 33: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 33

The MSSM Higgs sector in a tiny Nut Shell SUSY: 2 Higgs doublets 5 physical bosons

real MSSM: 2 CP even h, H, 1 CP odd A, charged H+, H-

at Born level 2 parameters: tan, m A mh < MZ

large loop corrections from SUSY breaking parameters

mh < 133 GeV for mtop=175 GeV, MSUSY=1TeV

corrections depend on 5 SUSY parameters: Xt, M0 , M2, Mgluino,

fixed in the benchmark scenarios e.g. MHMAX scenario

maximal Mh conservative LEP exclusion

t b/ W/Z

h cossin -sincos sin()

H sinsin cos/cos cos()

A cot tan -----

gMSSM = gSM

• no coupling of A to W/Z

• small small BR(h,bb)

• large large BR(h,H,A,bb)

= mixing btw. CP-even neutral Higgs bosons

Page 34: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 34

Discovery Potential in the tanversus MA Plane

LEP tan exclusion:

no exclusion for mt larger ~183 GeV !TEVATRON:

so far exclusion for tan > 50 MA<200GeV

calculations with FeynHiggs (Heinemeyer et al.)

no systematic uncertainties yet

main questions for ATLAS: At least 1 Higgs boson observable in the entire parameter space? How many Higgs bosons can be observed? Can the SM be discriminated from extended Higgs sectors?

4 CP conserving benchmark scenarios considered: Carena et al. , Eur.Phys.J.C26,601(2003)

1) MHMAX 2) No mixing 3) Gluophobic 4) small

conclusions the same due to to complementarity of search channels

Mtop=174.3 GeV

Page 35: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 35

h or H observable

with 30 fb-1

Vector Boson Fusion: 30 fb-1

studied for MH>110GeV at low lumi running

Page 36: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 36

Light Higgs Boson h

large area covered by several channels sure discovery and parameter

determination possible

small area uncovered @ mh ~ 95 GeV

300 fb-130 fb-1

VBF dominates observation

small area from bbh,H

for small Mh

Page 37: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 37

Heavy Neutral Higgs Bosons

large tan: bbH/A, H/A

~ (tan)2

ATLAS 30fb-1

low mass<450GeV: lep. had.

trigger on lepton

large mass > 450GeV: also had. had.

larger rate, trigger on hard tau jets

Eff.(LV1TR)= 80% =95% offline selected events

Tau ID: eff(tau)=55% rejection(QCD)=2500

H/A

Page 38: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 38

Overall Discovery Potential: 300 fb-1

at least one Higgs boson

observable for all parameters

in all CPC benchmark scenarios

significant area where only lightest Higgs boson h is observable

questions for future studies:

can SUSY decay modes

provide observation?

e.g.: H/A2 LSP + 4 lept.

ongoing study in BN (N. Möser)

similar results in other benchmark scenarios

VBF channels , H/Aonly used with 30fb-1

300 fb-1

Page 39: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 39

ATLASprel.

300 fb-1

SM or Extended Higgs Sector e.g. Minimal SUSY ?

discrimination via rates from VBF

R = BR(h WW) BR(h )

assume Higgs mass well measured no systematic errors considered

compare expected

measurement of R in MSSM

with prediction from SM

for same value of MH

=|RMSSM-RSM|exp

Page 40: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 40

The Higgs Sector in the CP Violating MSSM

mass eigenstates H1, H2, H3

<> CP eigenstates h,A,H

at Born level: CP symmetry conserved in Higgs sector

complex SUSY breaking parameters introduce new CP phases

mixing between neutral CP eigenstates

no a priori reason for real SUSY parameters complex pars. new sources of CP violation el.-weak baryogenesis in complex MSSM ok evade constraints from dipole moments via

cancellations of different terms or split SUSY

Why consider such scenarios?

M. Carena, M. Quiros, C.Wagner’98

Page 41: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 41

Phenomenology in the CPX scenario

H1,H2, H3 couple to W,Z

all produced in VBF

H3

H2

H1

H2,H3 H1H1, ZH1,WW, ZZ

decays possible

no limit for mass of H1 from LEP

(compare CPC MSSM: Mh>MZ

maximise effect CPX scenario (Carena et al., Phys.Lett B495 155(2000))

arg(At)=arg(Ab)=arg(Mgluino)=90 degree

scan of Born level parameters: tan and MH+-

LHWG-Note 2004-01

Page 42: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 42

CP-Violating MSSM: Overall Discovery Potential

MH1: < 70 GeVMH2: 105 to 120 GeV

MH3: 140 to 180 GeV

small masses below 70 GeVnot yet studied in ATLAS

300 fb-1

most promising channel: tt bW bH+, H+W H1, H1bb

final state: 4b 2j l same as ttH, Hbb (study in Bonn)

revised studies for H2/3H1H1 also interesting

yet uncovered area size and location of „hole“ depends on Mtop and program for calculation

Page 43: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 43

Very First look at new promising MC study

M H+ =135 GeV, MH1=54GeV, tan=4.8 (diploma thesis M. Lehmacher)

estimate of background seems difficults

coverage of hole area under study!

signal

ttjj

ttbb

t tH+ b W b H+W H1 H1bb

1 leptonic W decay lepton for trigger

reconstruct top quarks combinatorics

associate b quarks to H1, H+ MH1 and M H+

Page 44: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 44

Conclusion and Outlook

Standard model: discovery of SM Higgs boson with 15 fb-1

• requires good understanding of whole detector• multiple channels with larger luminosity Higgs profile investigaton

CP conserving MSSM: at least one Higgs boson observable • only h observable in wedge area at intermediate tan• maybe Higgs to SUSY or SUSY to Higgs observable?• discrimination via Higgs parameter determination seems promising

CP violating MSSM: probably a „hole“ with current MC studies• promising MC studies on the way

more realistic MC studies: • influence of miscalibrated and misaligned detector• improved methods for background estimation from data• use of NLO calcluations and MCs for signal and background

additional extended models + seach channels:• CPV MSSM, NMSSM, 2HDM• Higgs SUSY, SUSYHiggs• VBF, Hbb (b-trigger at LV2), VBF,Hinv. (add. forward jet trigger)

Page 45: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 45

Let‘s wait and work for Higgs boson discovery ….

Thanks for your attention!

Page 46: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 46

Backup slides

Page 47: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 47

Evidence for Spin 0 in H->WW->ll mode

between leptons

W from H opposite spins leptons same direction

+ add. BG normalisation

MT>175 GeVMT<175 GeV

Signal Region

Outside Signal Region

Background estimate for VBF, HWW

mT(ll) with (left) and w/o (right) lepton cuts

background estimation at level of 10% from data + shape from MC

ATLAS

Transverse mass

Page 48: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 48

CP even Spin 0: Measurement of Rates

Simultaneous fit of signal rates x BR in all 13 channels

Takes into account: cross talk between channels (e.g. GF events selected in VBF analysis) statistical fluctuations detector effects: Lumi, eff. tau, b-, forward jet tagging, and e background estimates: sidebands + shape + theoretical prediction uncertainties to signal rate from PDFs and QCD corrections

Page 49: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 49

Overview of 13 Channels used in new ATLAS Study

Production Decay Mass range

Gluon fusion

HHZZ4l HWW(*) l l

110 – 150 GeV 120 – 200 GeV 110 – 200 GeV

Vector Boson Fusion*

HH HWW(*)l lHZZ4l

110 – 150 GeV 110 – 150 GeV 110 – 190 GeV 110 – 200 GeV

ttH

HHbbHWWl l

110 – 120 GeV 110 – 140 GeV 120 – 200 GeV

WHHHWWl ll

110 – 120 GeV 150 – 190 GeV

ZH H 110 – 120 GeV* only studied for low lumi running, L= 30fb-1

Page 50: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 50

Higgs invisible particles

need confirmation by full simulation study

VBF assumes trigger on forward jets, not yet implemented

Page 51: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 51

Higgs self coupling

Page 52: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 52

The four CPC Benchmark Scenarios

Carena et al. , Eur.Phys.J.C26,601(2003)

Gluophobic scenario small gh,gluon mh < 119 GeV

Small scenario small ghbb and gh mh <123 GeV

MHMAX scenario maximal mh < 133 GeV conservative LEP exclusion

Nomixing scenario small mh < 116 GeV difficult for LHC

theo. goal: harm discovery viagg h, h and hZZ4 l

theo. goal: harm discovery viaVBF, h tth, hbb

Page 53: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 53

Signal and Background Rates

LO with CTEQ5L (no K-factors!)

running b-quark mass for bbh(/H/A) and gbtH+

1) SM production cross sections times MSSM correction factors (FH)

2) branching ratios from FeynHiggs

3) efficiencies and background expectations from documented MC studies

Mt= 175 GeV used for now

Page 54: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 54

4) for part of MSSM parameter space: large tot MSSM = K SM

K =

Corrections to Expected Signal Rates

5) signal overlap due to mass degeneracy of Higgs bosons

count signal in mass window 1

= signal 1 + signal 2 in window 1

h

Page 55: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 55

MC Studies with Discovery Potential

channel lumi mass range publication

VBF, HWW low M>110 GeV SN-ATLAS-2003-024

ttH, Hbb * low+high M>70GeV ATL-PHYS-2003-003

bbH/A low+high 70<M<135GeV

M> 120 GeV

ATL-PHYS-2002-021

ATL-PHYS-2000-005

bbH/Alep.had

had. had.

low

low

M >120 GeV

M > 450 GeV

ATL-PHYS-2000-001 ATL-PHYS-2003-009

ATL-PHYS-2003-003

WWll low+high 140<M <120GeV ATL_PHYS-2000-015

H low+high M > 70 GeV TDR

ZZ4l low+high M > 100 GeV TDR

AZhllbb, Hhhbb

low+high 60 <ML<130 100<MH<360

TDR TDR

H/Att low+high M > 350 GeV TDR

gbtH+-, H,tb low+high M >180 GeV SN-ATLAS-2002-017

ttbW bH+-, H+- low M < 170 GeV ATL-PHYS-2003-58/TDR

*ttH, Hbb at high. lumi see MSSM note

Page 56: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 56

almost same conclusion

for all 4 CP conserving

benchmark scenarios

Vector Boson Fusion: 4 CPC scenarios

Page 57: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 57

Light Higgs Boson h: 30 fb-1

difference mainly due to

different mh in same (tan,MA) point

( up to 17 GeV difference)

observable channels: VBF bbh h tth hbb

Page 58: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 58

Small scenario, h: 30 fb-1

• covered by enhanced BR to gauge bosons

• complementarity of search channels

almost gurantees observation of h

•hole due to reduced branching ratio for H

Page 59: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 59

Light Higgs Boson h: 300 fb-1 (VBF only 30 fb-1)

also hgg, hZZ4 leptons, tthbb contribute

large area covered by several channels

sure discovery and parameter determination possible

small area uncovered @ mh = 90 to 100 GeV hsensitive in gluophobic scenario due to Wh, tth production

Page 60: Higgs Physics with ATLAS

Markus Schumacher Higgs Physics with ATLAS Wuppertal, November 10th 2005 60

Charged Higgs Bosons

gbH+-t

H+-

tbqq

low mass: mH+-< mtop

ggttttH+-bWonly low lumi.

new:

Wqq

H+-

high mass: mH+-> mtop

transition region around mtop

needs revised experimental analysis

running bottom quark mass used

Xsec for gbtH+- from T. Plehn‘s program