Tony Doyle on behalf of the ATLAS Collaboration

Old World

NewWorld

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NewWorld

1831 French Foreign Legion.. Marche ou crève.. Standard Model?

Old World

1830 French Revolution.. Trois Glorieuses.. Three Glorious signals..

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References: arXiv:1307.1427 Sub. Phys. Lett. B (Couplings)

arXiv:1307.1432 Sub. Phys. Lett. B (Spin) ATLAS-CONF-2013-012 (γγ) ATLAS-CONF-2013-013 (ZZ*) ATLAS-CONF-2013‐031 (WW*) ATLAS-CONF-2013-040 (Spin) ATLAS-CONF-2013-079 (VH → bb) ATLAS-CONF‐2012‐160 (H → tt) ATLAS-CONF-2013‐075 (WW*) ATLAS-CONF-2013-029 (γγ)

“Do you hear the people sing Lost in the valley of the night?

It is the music of a people Who are climbing to the light.”

Victor Hugo, Les Misérables

• H→ γγ, ZZ*, WW* analysis updates based on full 2011-2012 dataset (4.6 fb-1 @ 7TeV, 20.7 fb-1 @ 8TeV) • Higgs mass from H→γγ and H→ZZ*→4l • Signal strengths (m) • Sensitivity to vector boson fusion (VBF) • Comparison of decay rates • Couplings • Spin and parity

• Attempting to blow out the Higgs Standard Model candle..

Observed (√s=8 TeV,

mHrec = 126.8 GeV ±2s)

<Expected purity> s/s+b (√s=8 TeV)

Main backgrounds ∫Ldt (√s=7 & 8 TeV)

13931 370/13575 = 2.7% gg,gj and jj 4.8 & 20.7 fb-1

H → gg Update Since “Discovery Paper”

Phys. Lett. B 716 (2012) 1-29

arXiv:1307.1427 (Submitted to Phys. Lett. B on 4 Jul 2013)

SM expectation: σvis ~ 20 fb with relatively low experimental purity ~ 3% (√s=8 TeV) Simple signature: two high-pT isolated photons - ET (γ1, γ2) > 40, 30 GeV (√s=8 TeV) Main background: γγ continuum (irreducible, smooth, ..) as well as gj and jj Events divided into categories based on η-photon (e.g. central, rest, …)

converted/unconverted, pTγγ along thrust axis (varying s/b)

Events divided into ggF or VH (lepton+ETmiss) or VBF (two-jet) categories (√s=8 TeV)

Main channel with sensitivity to VBF production Significance 7.4s (4.3s expected), mass resolution 1.4 – 2.5 GeV

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SM expectation: σvis ~ 1.3 fb with high experimental purity ~ 60% Good lepton reconstruction and identification: pT1, pT2, pT3, pT4 = 20, 15, 10, 7 (6) GeV for e (m) Good lepton energy/momentum mH

rec resolution: 4m, 2e2m, 4e = 1.6, 1.9, 2.4 GeV Good control of reducible backgrounds (Zbb, Z+jets, tt) in low-mass region: cannot rely on MC alone (theoretical uncertainties, b/q-jet lepton modelling, ..) need to compare MC to data in background-enriched control regions (but low statistics ..) Divided into ggF or VBF (two-jet, Dh > 3, mrec > 350 GeV) or VH (addl. lepton ) categories Significance 6.6s (4.4s expected), mass resolution 1.6 – 2.4 GeV (with mZ constraint)

H → 4l

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arXiv:1307.1427

Observed (mH

rec = 125 ±5 GeV)

Expected purity s/s+b(√s=7&8 TeV)

Main backgrounds ∫Ldt (√s=7 & 8 TeV)

32 15.9/27.2 = 58% ZZ, Z+jets, top 4.6 & 20.7 fb-1

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Ldtò

H → WW(*)

SM expectation: σvis ~ 7 fb with experimental purity ~ 13% (√s=8 TeV) ee,eµ,mm + 2ν final state: two isolated opposite-sign leptons, large ET

miss Challenging: 2ν “counting channel” Njet classification (0,1, >= 2 jet) to separate ggF and VBF (2%, 1%, 81%) processes Main backgrounds: WW, Wt, top, W+jets, Z+jets mll ≠ mZ, b-jet veto, … Topological cuts against “irreducible” WW bkgd: pTll, mll, Δϕll (smaller for scalar Higgs), mT (ll, Et

miss(rel))

Significance 3.8s (3.8s expected) for assumed mH = 125.5 GeV (mHWW ~ 140 ± 15 GeV)

~80% of overall significance from em channel (DY background for ee and mm channels)

Observed (Njet = 0, 1, >=2)

Expected purity s/s+b (√s=8 TeV)

Main backgrounds ∫Ldt (√s=7 & 8 TeV)

831, 309, 55 152/1188 = 12.8% WW, Wt, W+jets,

top, etc… 4.6 & 20.7 fb-1

arXiv:1307.1427

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Common

H → ZZ(*) → 4l (statistics)

H → WW(*) → lnln

(theory + modelling)

H → gg (theory+modelling)

Systematics

• Combine γγ and 4l mass measurements • Signal strengths, μγγ and μ4l, allowed to vary

independently • Don’t assume SM couplings (but ratio constrained)

• DmH=2.3 +0.6-0.7(stat) ±0.6 GeV • 2.4s deviation

• H → WW consistent

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H → ZZ(*) → 4l H → gg

Higgs Mass

mH=125.5 ± 0.2 (stat) +0.5-0.6 (sys) GeV

See talk by Yohei Yamaguchi

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Signal Strength Signal strength μ = σ/σSM Combination of diboson final states H → γγ H → ZZ(*) → 4l H → WW(*) → lνlν measured assuming mH=125.5 GeV • Variation due to mH uncertainty: ±3%

• Compatibility with SM (μ=1): 7%

• Largest deviation μγγ: 1.9 s Including preliminary μbb, μττ: μ=1.23 ± 0.18 ATLAS also sets preliminary (95%CL) limits: H → μμ: μ<9.8 (20.7 fb-1) H → Zγ: μ<18.2 (4.6 fb-1 + 20.7 fb-1)

μ = 1.33 ± 0.14 (stat) ± 0.15 (sys) ± 0.11 (theo)

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Process s (pb) ± scale ± PDF

ggF 19.5 ± 1.5 ± 1.5

ttH 0.13 ± 0.008 ± 0.008

VBF 1.58 ± 0.01 ± 0.06

VH 1.09 ± 0.01 ± 0.04

Vector Boson-Higgs coupling: μVBF+VH ≡ μVBF = μVH

Fermion-Higgs coupling: μggF+ttH ≡ μggF = μttH

stot = 22.3 ± 1.5 ± 1.5

Higgs Production <x> = 1/64=0.016; mH = 125 GeV, √s = 8 TeV

Cross section dominated by ggF: Explore sensitivity to VBF (and VH) via data Associated H→gg+jet (and H→WW*+lepton) production Now constrained by H → gg Njet (+ jet veto fractions , pT) Higgs new dawn of s measurements

87%

1% 7%

5%

ggF

ttH

VBF

VH

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VBF Production

μVBF+VH vs μggF+ttH potentially modified by B/BSM

Good agreement with SM 3.3s evidence for VBF production (driven by H → γγ)

μVBF+VH / μggF+ttH = 1.4+0.4-0.3(stat)+0.6-0.4(sys)

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Process BR ± 5% rel. unc.

H → gg 2.28 x 10-3

H → ZZ(*) → 4l 1.25 x 10-4

H → WW(*) → lnln 0.01 e.g. H → gg

where kg and kγ are loop coupling scale factors

and kH is the total Higgs boson width scale factor

Assume single narrow resonance: σ·BR(ii→H→ff) = σii·Γff / ΓH Test modifications to couplings magnitude: CP even scalar at this stage Not all couplings accessible with current data, so test 5 benchmark models (LHC-XS-WG)

+ -

Higgs Decay, mH = 125.5 GeV

Functions of kt, kW,...:

(8)

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Coupling Measurements

Sensitivity to couplings, ki, given sij

ggH, Gijgg and GSM

ff from theory Equation represents dominant contributions only Test various benchmark models using the profile likelihood ratio, L(k) kj treated as parameters of interest or nuisance parameters

+ -

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Coupling to fermions and bosons kF for fermions kV for bosons (kV > 0 assumed, some sensitivity to +ve sign via t+W interference, mainly from H →gg decay loops)

kF ∈ [0.76, 1.18] (68% CL)

2D Compatibility with SM: 12% kF mainly via gg → H loop Assumes no contribution from BSM particles If SM constraint relaxed, can constrain the ratios lFV = kF /kV or kVV = kVkV/kH

kV ∈ [1.05, 1.22] (68% CL)

lFV ∈ [0.70, 1.01] (68% CL)

kVV ∈ [1.13, 1.45] (68% CL)

Model 1

Model 2

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Ratio of W/Z couplings Fermion couplings grouped together,

total width left free lWZ = kW /kZ (SM lWZ = lFV = kZZ = 1)

lFV = kF /kV (profiled in fit) kZZ = kZ kZ/kH (profiled in fit)

Simplest method from measured H → WW* and H → ZZ* rates with μggF+ttH . B(H → ZZ*)/BSM(H → ZZ*) and μggF+ttHμVBF+VH/μggF+ttH profiled: Slightly improved sensitivity using WH and ZH (VBF) production (75% W-fusion: 25% Z-fusion) as well as H → γγ rate 3D Compatibility with SM: 19% Removing H → γγ rate and adding lgZ = kg /kZ to absorb possible BSM effects 4D Compatibility with SM: 20%

lWZ ∈ [0.61, 1.04] (68% CL)

lWZ =0.81+0.16-0.15

lWZ =0.82 ± 0.15 lFZ > 0 lFZ < 0

lWZ2 = B (H → WW*)/B (H → ZZ*)

BSM(H → WW*)/BSM(H → ZZ*)

Model 3

Model 4

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Constraints on BSM loops and Summary

New heavy particles may contribute to loops • Assume negligible contribution to width • Assume SM particles have SM couplings Effective scale parameters kg and kg

2D Compatibility with SM: 14%

kg =1.04 ± 0.14 kg =1.20 ± 0.15

Couplings tested for anomalies w.r.t. fermion and boson, W/Z and vertex loop

contributions at ±10-15% precision • Consistent with SM

Model 5

Combined Spin Analysis

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Alternative spin-parity hypotheses 0-, 1+, 1-,2+

tested compared to o+

Models generated using JHUGen (Gao et al: arXiv1001.3369) Use discriminants sensitive to spin

and parity

Process JP test Discriminants

H → gg 2+m mgg |cos q*|

H → ZZ* → 4l 0-, 1+, 1-, 2+m e.g. cos q1 m34

→ BDT (MELA)

H →WW*→ enmn 1+, 1-, 2+m e.g. mem Dfem

→ BDT

e+ m-

J = 1 → 1+1 ruled out (Landau Yang theorem)

2+m Graviton-inspired tensor

with minimal SM couplings chosen

(ggF production polarisations ± 2, qq annihilation ± 1)

Full reconstruction of 4l final state Five angles q1, q2, q *, F1, F and two masses m12(mZ

rec), m34(mZ*rec)

Reduced background for em channel

Combine all three channels to maximise

sensitivity

H → gg Spin Analysis

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122 < mgg < 130 GeV

- Simultaneous fit to mgg and |cos q*|

- |cos q*| for spin and mgg to control background

- Large background derived from sideband data

- Optimised cuts (pTg1 > 0.35 mgg and pT

g2 > 0.25 mgg )

- Residual correlations at 0.6% (2%) level for |cos q*| < (>)0.8

- Correction for gg → γγ bkgd + Higgs spin-0 interference esp. for |cos q*| > 0.8

(none available for 2+ hypothesis)

Collins-Soper Frame (Higgs Rest Frame)

105 < mgg < 122 GeV 130 < mgg < 160 GeV

observed

p0(2+)

p0(0+)

General Approach

- Binned likelihood using discriminants

e.g. mgg and |cos q*|

- Poisson probability given a

signal S scaled by strength m

and background B with

nuisance parameters q and constraints from auxiliary

measurements A for each channel

Ratio of likelihoods test statistic

q = log(L (0+)/L (JPalt))

with m fixed for a given JP

- Exclusion using CLS

CLS = p0 (JP

alt) / (1-p0(0+))

- Observed 2+ exclusion 99.3% (1-CLS)

H gg Spin Analysis 0+ vs 2+ after background subtraction

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Comprehensive analysis vs qq fraction (4% in LO QCD, but higher-order corrections possible):

H → 4l Spin Analysis

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0+ vs 0-

0+ vs 1+

- BDT using five angles and two masses

- BDT trained and evaluated separately for each hypothesis

- 115 < m4l < 130 GeV

- Statistics limited, but sensitive to each JP

- High purity (121 < m4l < 127 GeV) and lower purity

{115 < m4l < 121 GeV, 127 < m4l < 130 GeV} evaluation

Observed 0- exclusion 97.8% Observed 1+ exclusion 99.8%

H → WW* Spin Analysis

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- Sensitive to 1+, 1-, 2+m via shapes

- Reduced background for em events

- BDTs using mem , Dfem , pTem , mT

em

- Detailed study of inputs and correlations

- WW background evaluated from data control regions

- Two BDTs are used to distinguish (a) 0+ from JPalt and (b) 0+ from the sum of backgrounds

- (BDT histograms are 1-D mapping of 2-D distributions with bins ordered by increasing signal)

Observed 2+ (qq=0%) exclusion 95.2% Observed 2+ (qq=100%) exclusion 99.96%

Increasing signal expected

0+

2+ (qq=100%)

Combined Spin Analysis

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H gg largest contributions H → WW*

- Combined 2+m exclusions at 3-4s level

- Combined exclusions generally at 2-3s level

- All observations consistent with SM Higgs Boson

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“Do you hear the people sing Lost in the valley of the night?

It is the music of a people Who are climbing to the light.”

Victor Hugo, Les Misérables

• Important diboson measurements now submitted at √s = 7 and 8 TeV

• H→ γγ, ZZ*, WW* • Results consistent with SM • mH from H→γγ and H→ZZ*→4l :

• Signal strength:

• Evidence for vector boson fusion (VBF)

at 3.3s level • Couplings tested: fermion and boson,

W/Z and vertex loop contributions at ±10-15% precision

• Spin and parity: combined exclusions for 0-, 1+, 1-,2+

generally at 2-3s level • A Higgs Boson is born

• Early days, but the Standard Model first birthday candle is proving difficult to blow out..

mH=125.5 ± 0.2 (stat) +0.5-0.6 (sys) GeV

μ = 1.33 ± 0.14 (stat) ± 0.15 (sys) ± 0.11 (theo)

Backups

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ATLAS-CONF-2013-079

- Require 2 b-tags and distinguish 0, 1, 2 lepton

channels

- Diboson fit where theoretical uncertainties are

constrained

- Higgs discrimination based on mbb, resolution of

~16%, improved by including muons and partial

neutrino correction

Also 7 TeV analysis of tt+H, with

H bb [ATLAS-CONF-2012-135]

m (125 GeV) = 0.2 ± 0.5(stat) ± 0.4(syst)

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VH production with H bb

Combined limit 1.4 x SM (1.3 expected):

ATLAS-CONF-2013-079, see talk by Jason Lee

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Signal Strength Latest combination of five final states W, Z H → bb H → tt Including preliminary μbb, μττ: μ=1.23 ± 0.18

H → gg associated jet production cross sections

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Initial state jet radiation used to constrain production mechanism Higgs new dawn of s measurements

ATLAS-CONF-2013-029, see talk by Giovanni Calderini

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Process s (pb) ± scale ± PDF

ggF 19.5 ± 1.5 ± 1.5

ttH 0.13 ± 0.008 ± 0.008

VBF 1.58 ± 0.01 ± 0.06

VH 1.09 ± 0.01 ± 0.04

Vector Boson-Higgs coupling: μVBF+VH ≡ μVBF = μVH

Fermion-Higgs coupling: μggF+ttH ≡ μggF = μttH

stot = 22.3 ± 1.5 ± 1.5

Higgs Production mH = 125 GeV, √s = 8 TeV

Cross section dominated by ggF: Explore sensitivity to VBF (and VH) via data Associated 2-jet (and lepton) production e.g. H → gg simulation breakdown by categories

87%

1% 7%

5%

ggF

ttH

VBF

VH

Main 4l Mass Scale systematic uncertainties:

Further investigation and extensive checks have not led to additional substantial sources of systematic uncertainty: - Measurement with MS and ID alone - Local detector biases checked event by event - Local resolution effects checked using event- by-event error; - kinematic distributions in agreement with expectation - FSR simulation - Different mass reconstruction using Z-mass constraint (+400 MeV shift)

Source Relative Mass Scale Effect

Absolute Energy scale calibration from Z

0.4%

Low transverse energy electrons

0.2%

Muon momentum scale 0.2%

Main Mass Scale systematic uncertainties: Further investigation and extensive checks lead to additional sources of systematic uncertainties: - LAr Strips relative calibration (0.2%) - Photon energy resolution (0.15%) - Calibration of the high gain (0.15%) - Mis-classification due to fake conversions (0.13%) - Backgound modeling (0.1%) - Lateral shower development simulation (0.1%) - Effect of PV choice (0.03%)

Source Relative Mass Scale Effect

Absolute Energy scale calibration from Z

0.3%

Upstream material simulation inaccuracies

0.3%

Pre-Sampler energy scale

0.1%

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H gg and H 4l Mass Scale Systematic Uncertainties

h

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5

Re

lative

mass s

ca

le d

iffe

ren

ce

-0.005

-0.004

-0.003

-0.002

-0.001

0

0.001

0.002

0.003

0.004

0.005

Data 2012

mm ®Z

mm ® U

mm ® yJ/

ATLAS Preliminary

[GeV]12m

50 60 70 80 90 100

[G

eV

]m

4m

90

95

100

105

110

115

120

125

130

135

= 124 GeVHm

= 8 TeV)sData (

PreliminaryATLAS

[GeV]12m50 60 70 80 90 100

[G

eV

]3

4m

20

30

40

50

60

70

80=125 GeVHm

<130 GeV)4l

Bkg (120<m

<130 GeV)4l

Data (120<m

PreliminaryATLAS

4l(*)

ZZH-1

Ldt = 4.6 fbò = 7 TeV: s

-1Ldt = 13.0 fbò = 8 TeV: s

[GeV]m4

m

70 75 80 85 90 95 100 105

Even

ts/3

GeV

20

40

60

80

100ATLAS Preliminary

= 7 TeV: s

= 8 TeV: s

ò

ò

-1Ldt = 4.6 fb

-1Ldt = 13.0 fb

Data(*)

ZZtZ+jets,t

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Main systematics on Yield and Migration

Theory (PDF, scales, as) ~12% (overall)

g Efficiency 5.3%

Background Model ~3%

Luminosity 3.9% and 3.6%

Trigger 0.5%

Isolation 1%

Energy Scale 0.5%

JES 4% - 19% (HM 2-jets)

pTt Modelling 0.8%

Material mis-modelling ~4%

UEPS 7% - 30% (LM HM 2-jets)

Leptons ~2%

32

H gg Normalization Systematic Uncertainties

33

VH Vbb

H τ τ

Mild excess of 2.2 s building up • Coherent picture between the sub

channels Z(ll)H(bb); Z(nn) H(bb); W(ln) H(bb) need more statistics

VH Vτ τ

Very mild excess is building up at 1.3 s level

HIG-12-044

HIG-12-051

HIG-12-043

Very small contribution

All including VH

Fermions

Signal (SM) Signal purity

s/b Main

backgrounds Production 7 & 8 TeV

~330 0.3% - 30% ZZ, Z+jets, top VBF, Hgg, VH 4.9 & 13 fb-1

tt channel basic facts sheet :

Ldtò

H thadthad candidate in VBF channel (mMMC = 131 GeV)

H ττ Reoptimised 7+8 TeV analysis

ATLAS-CONF-2012-160

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- Search in exclusive categories: lep-lep, lep-had, had-had and

jets: 0, 1 (boosted or not), 2 (VBF, VH)

- Use of MMC mass

m(125) = 0.7 ± 0.7

95% CL limit (125): 1.9 [ exp: 1.2 ] × SM

Significance (125): 1.1σ [ exp: 1.7σ ]

s(m) = 13% ~ 20%

- Most powerful channel VBF

- Background modeling is critical

especially in specific environments

such as VBF production : Use

embedding

H ττ Reoptimised 7+8 TeV analysis

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Signal (SM) Signal purity

s/b Main backgrounds Production 7 & 8 TeV

~50 ~1% - 10% Wbb,Zbb, top, etc… VH 4.9 & 20 fb-1

VH(bb) channel basic facts sheet :

Ldtò

VH production with H bb Combined and reoptimised 7+8 TeV analysis

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A.Djouadi Phys.Rept.457:1-216 Huge progress in theory: signals and (complex) backgrounds Major achievement of the theory community; very fruitful

discussions with the experiments (e.g. through LHC Higgs x-sn WG,LPCC..)

GF H → WW , ZZ , γγ , bb,tt

VBF H → WW, ZZ , γγ , tt

H → WW, γγ, bb

H → WW, γγ, bb

Typical uncertainties on cross-section gg +15 -20 % NNnLO VBF 5% NLO WH,ZH 5% NNLO ttH 15% NLO

These production cross sections are used with the decays bb , tt , WW , ZZ , gg

Inner Detector (|h|<2.5, B=2T): Si Pixels, Si strips, Transition Radiation detector (straws) Precise tracking and vertexing, e/ separation Momentum resolution: s/pT ~ 3.8x10-4 pT (GeV) 0.015

Length : ~ 44 m Radius : ~ 12 m Weight : ~ 7000 tons ~108 electronic channels 3000 km of cables

Muon Spectrometer (|h|<2.7) : air-core toroids with gas-based muon chambers Muon trigger and measurement with momentum resolution < 10% up to Em ~ 1 TeV

EM calorimeter: Pb-LAr Accordion e/g trigger, identification and measurement E-resolution: s/E ~ 10%/E

HAD calorimetry (|h|<5): segmentation, hermeticity Fe/scintillator Tiles (central), Cu/W-LAr (fwd) Trigger and measurement of jets and missing ET E-resolution: s/E ~ 50%/E 0.03

3-level trigger reducing the rate from 40 MHz to ~200 Hz

38 Countries 174 Institutions

3000 Scientists 1000 Students

ATLAS Detector

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