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Study of the Tensor Structure of Higgs BosonCouplings with the H → ZZ∗ → 4ℓDecay Channel with the ATLAS DetectorIMPRS Young Scientist Workshop at Ringberg Castle
Verena WalbrechtMax Planck Institute for Physics(Werner-Heisenberg-Institut)
July 17th, 2017
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
The Standard Model is not the End of the Story...
Open questions:– General relativity– Neutrino oscillations– Nature of dark matter and dark energy– Matter - antimatter asymmetry
Theories beyond the Standard Model:– Supersymmetry, string theory, M-theory and extra dimensions
Experimental search for physics beyond the Standard Model in pp collisions:
1. Direct searches: search for new particles (heavy resonances, SUSYparticles, dark matter ...)
2. Indirect searches: precise measurements of known particles of the SM -search for deviations from the prediction of the SM⇒ Search for anomalous Higgs boson couplings
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 2/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
The Higgs Boson in the Standard Model2012: discovery of the Higgs boson
SM prediction: scalar CP-evenparticle (JP=0+)
Conjugation scalar
Spin: J 0Charge: C +1Parity: P +1
JP 0+
SM Higgs boson Spin 0+ hypotheses preferred bythe Run I data
But: small admixtures of 0− state to 0+ are still possible (Beyond SM):
|HBSM⟩ = cos(α)|0+⟩+ sin(α)|0−⟩
CP-even
[GeV]4lm100 150 200 250
Events
/5 G
eV
0
5
10
15
20
25
1Ldt = 4.8 fb∫ = 7 TeV: s
1Ldt = 5.8 fb∫ = 8 TeV: s
4l→(*)ZZ→H
Data(*)
Background ZZ
tBackground Z+jets, t
=125 GeV)H
Signal (m
Syst.Unc.
ATLAS
Question
: Isit a
SMHigg
s boson
?
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 3/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Measurement of the Higgs Boson CP Properties
1. Decay Channel for CP properties measurement:
2. Observable to study CP properties:
)1θcos(1− 0.5− 0 0.5 1
Ent
ries
/ 0.2
50
2
4
6
8
10
12
14
16
18 ATLAS
4l→ZZ*→H-1 = 7 TeV, 4.5 fbs
-1 = 8 TeV, 20.3 fbs
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
3. Approach to account for BSM contributions: effective field theory
⇒ Statistics very low: using event rates
Z∗
Z
H
`+
`−
`+
`−
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Measurement of Anomalous CouplingsEffective field theory assumption:
– Physics beyond the SM appears at energy scale Λ≫ E⇒ Point-like interaction can be assumed
LV0 =
{κSM cosα
[12gHZZZµZ
µ + gHWWW+µW
−µ]
− 1
4
[κHgg cosα gHggG
aµνG
a,µν + κAgg sinα gAggGaµνG
a,µν]
− 141Λ
[κHZZ cosα ZµνZ
µν + κAZZ sinα ZµνZµν]
− 121Λ
[κHWW cosαW+
µνW−µν + κAWW sinαW+
µνW−µν
]}X0
X0
Z⇤
Z
g
g
X0
Z∗
Z
κHgg, κAgg κSM, κAZZ, κHZZ
1. non-SM coupling to gluons 2. non-SM coupling to vector bosons
SM CP-evenanomalous (BSM) CP-evenanomalous (BSM) CP-odd
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 5/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Measurement of Anomalous CouplingsEffective field theory assumption:
– Physics beyond the SM appears at energy scale Λ≫ E⇒ Point-like interaction can be assumed
LV0 =
{κSM cosα
[12gHZZZµZ
µ + gHWWW+µW
−µ]
− 1
4
[κHgg cosα gHggG
aµνG
a,µν + κAgg sinα gAggGaµνG
a,µν]
− 141Λ
[κHZZ cosα ZµνZ
µν + κAZZ sinα ZµνZµν]
− 121Λ
[κHWW cosαW+
µνW−µν + κAWW sinαW+
µνW−µν
]}X0
X0
Z⇤
Z
g
g
X0
Z∗
Z
κHgg, κAgg κSM, κAZZ, κHZZ
1. non-SM coupling to gluons 2. non-SM coupling to vector bosons
SM CP-evenanomalous (BSM) CP-evenanomalous (BSM) CP-odd
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 5/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Measurement of Anomalous CouplingsEffective field theory assumption:
– Physics beyond the SM appears at energy scale Λ≫ E⇒ Point-like interaction can be assumed
LV0 =
{κSM cosα
[12gHZZZµZ
µ + gHWWW+µW
−µ]
− 1
4
[κHgg cosα gHggG
aµνG
a,µν + κAgg sinα gAggGaµνG
a,µν]
− 141Λ
[κHZZ cosα ZµνZ
µν + κAZZ sinα ZµνZµν]
− 121Λ
[κHWW cosαW+
µνW−µν + κAWW sinαW+
µνW−µν
]}X0
X0
Z⇤
Z
g
g
X0
Z∗
Z
κHgg, κAgg κSM, κAZZ, κHZZ
1. non-SM coupling to gluons 2. non-SM coupling to vector bosons
SM CP-evenanomalous (BSM) CP-evenanomalous (BSM) CP-odd
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 5/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Analysis Strategy
Too low statistics to use the information from angular distributions⇒ Event rates
Approach: effective field theory
Too low statistics to measure all predicted couplings simultaneously⇒ Test two different models with different assumptions:
All other couplings are set to the SM value
X0
Z⇤
Z
g
g
X0
Z∗
Z
κHgg, κAgg κSM, κAZZ, κHZZ
1. non-SM coupling to gluons 2. non-SM coupling to vector bosons
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 6/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
1. Measurement of Hgg Tensor Coupling
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
κ2Hgg
κ2Agg
κ2SM
κ2SM
ggF
VBF
H → ZZ∗ → 4ℓ
Production:
Decay:σggF ∝ κ2
Agg
Dependence:
σVBF =const
Production rate information sensitive to BSM contributions
Production and decay rates are dependent on the anomalous couplings:
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 7/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
1. Measurement of Hgg Tensor Coupling
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
κ2Hgg
κ2Agg
κ2SM
κ2SM
ggF
VBF
H → ZZ∗ → 4ℓ
Production:
Decay:σggF ∝ κ2
Agg
Dependence:
σVBF =const
Production rate information sensitive to BSM contributions
Production and decay rates are dependent on the anomalous couplings:
)αsin(⋅Aggκ1− 0.5− 0 0.5 1
at L
O [p
b]σ
0
5
10
15
20
25
30
35
= 13TeVsMadGraph5_aMC@NLO at LO Standalone,
=16.5 pbggF,SMσ
=4.4 pbVBF,SMσ
ggF
σVBF,BSM=
VBF
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
2. Measurement of the HZZ Tensor Coupling
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
κ2Hgg
Effectivecoupling
κ2SM, κ2HZZ, κ
2AZZ
κ2SM, κ2HZZ, κ
2AZZ
ggF
VBF
H → ZZ∗ → 4ℓ
Production:
Decay:σggF ∝ κ2
XZZ
Dependence:
σVBF ∝ κ4XZZ
Production rate information sensitive to BSM contributions
Production and decay rates are dependent on the anomalous couplings:
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 8/14
Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
2. Measurement of the HZZ Tensor Coupling
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
κ2Hgg
Effectivecoupling
κ2SM, κ2HZZ, κ
2AZZ
κ2SM, κ2HZZ, κ
2AZZ
ggF
VBF
H → ZZ∗ → 4ℓ
Production:
Decay:σggF ∝ κ2
XZZ
Dependence:
σVBF ∝ κ4XZZ
Production rate information sensitive to BSM contributions
Production and decay rates are dependent on the anomalous couplings:
)α sin(⋅ AZZκ30− 20− 10− 0 10 20 30
at L
O [p
b]σ
0
5
10
15
20
25
30
35
= 13TeVsMadGraph5_aMC@NLO at LO Standalone,
=16.5 pbggF,SMσ
=4.4 pbVBF,SMσ
ggFVBF
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Event CategorisationProduction mode splitting for the SM Higgs bosonfor mH =125 GeV:
0 20 40 60 80 100
ttH enriched
VH-leptonic
VH-hadronic
VBF enriched
mixed
ggF enriched
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
H
W/Z
q
q
W/Z
H
g
g
t/b
t/b
H
ggF87.4%
VBF6.8%
VH4.0%
ttH1.8%
ggF VBF WH ZH ttH
0 jet
1 jet
≥ 2 jet, mjj>120 GeV
≥ 2 jet, mjj<120 GeV
≥ 1 additional ℓ
≥ 1 nb,jet and≥ 4 njet
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Signal ModellingContinuous signal model to describe signal expectation in dependence onBSM couplings (κAgg, κHZZ, κAZZ)
Predicts number of expected events at every parameter point based on adiscrete set of simulated input samples
Nout(κout) =∑Ninput
i=1 wi(κout; κi) · Ni(κi)
1. Hgg Tensor Coupling: κ = (κHgg, κAgg)
2. HZZ Tensor Coupling: κ = (κSM, κHZZ, κAZZ)
Output distribution weight Input distributionκ1
κ2
κout
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Results of the Tensor Coupling MeasurementMeasuring BSM coupling parameter:Comparison of observed number of events in each category with the onepredicted by signal model
118 GeV<m4ℓ<129 GeV (for SM Signal):
Event ggF mixed VH- VBF VH- ttH-Category enriched hadronic enriched leptonic enriched
Signal 26.80± 2.50 15.67± 1.33 3.54± 0.51 06.87± 0.81 0.32± 0.02 0.39± 0.04ZZ∗ 13.70± 1.00 04.12± 0.42 0.66± 0.16 01.17± 0.32 0.05± 0.01 0.01± 0.01Z+jets,tt 02.23± 0.31 00.96± 0.42 0.02± 0.02 00.45± 0.04 0.01± 0.00 0.07± 0.04Expected 42.70± 2.70 20.85± 1.41 4.39± 0.51 08.42± 0.91 0.38± 0.02 0.47± 0.05Observed 49.00± 0.00 24.00± 0.00 3.00± 0.00 19.00± 0.00 0.00± 0.00 0.00± 0.00
Test statistic:
q = −2 lnL(κ)L(κ)
= −2ln(λ)
L(κ): is the maximum of the likelihood
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Results of the Tensor Coupling MeasurementMeasuring BSM coupling parameter:Comparison of observed number of events in each category with the onepredicted by signal model
118 GeV<m4ℓ<129 GeV (for SM Signal):
Event ggF mixed VH- VBF VH- ttH-Category enriched hadronic enriched leptonic enriched
Signal 26.80± 2.50 15.67± 1.33 3.54± 0.51 06.87± 0.81 0.32± 0.02 0.39± 0.04ZZ∗ 13.70± 1.00 04.12± 0.42 0.66± 0.16 01.17± 0.32 0.05± 0.01 0.01± 0.01Z+jets,tt 02.23± 0.31 00.96± 0.42 0.02± 0.02 00.45± 0.04 0.01± 0.00 0.07± 0.04Expected 42.70± 2.70 20.85± 1.41 4.39± 0.51 08.42± 0.91 0.38± 0.02 0.47± 0.05Observed 49.00± 0.00 24.00± 0.00 3.00± 0.00 19.00± 0.00 0.00± 0.00 0.00± 0.00
Test statistic:
q = −2 lnL(κ)L(κ)
= −2ln(λ)
L(κ): is the maximum of the likelihood
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Results of the Hgg Tensor Coupling Measurement
Aggκ
1− 0.5− 0 0.5 1
)λ2
ln (
0
5
10
15
20
25
68% CL
95% CL
Observed
SM expected
ATLAS Preliminary
4l→ ZZ* →H 113 TeV, 36.1 fb
= 1SMκ = 1, Hggκ
| = 0.43AggκObserved: |
= 0.00AggκExpected:
BSM couplingparameter
Allowed range at 95% confidence level (CL)Best fit expected for SM observed
κAgg ±0.43 [-0.47,0.47] [-0.68,0.68]⇒ Compatible with the SM prediction within 1.8 standard deviations
κSM · cosα=1
κHgg · cosα=1Regionsexcludedat 95% CL
Expected and observed distributions of the test statistic q for fits of κAgg:
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Results of the HZZ Tensor Coupling Measurement
Avvκ
8− 6− 4− 2− 0 2 4 6 8
)λ2
ln (
0
5
10
15
20
25
30
68% CL
95% CL
Observed
SM expected
ATLAS Preliminary
4l→ ZZ* →H 113 TeV, 36.1 fb
= 1SMκ = 1, Hggκ
| = 2.9AvvκObserved: |
= 0.0AvvκExpected:
Hvvκ
6− 4− 2− 0 2 4 6
)λ2
ln (
0
5
10
15
20
25
30
68% CL
95% CL
Observed
SM expected
ATLAS Preliminary
4l→ ZZ* →H 113 TeV, 36.1 fb
= 1SMκ = 1, Hggκ
= 2.9HvvκObserved:
= 0.0HvvκExpected:
BSM couplingparameter
Allowed range at 95% confidence level (CL)Best fit expected for SM observed
κAZZ ±2.9 [-3.5,3.5] [-5.2,5.2]κHZZ 2.9 [-2.9,3.2] [0.8,4.5]
⇒ Compatible with the SM prediction within 1.4 and 2.3 standard deviations
Expected and observed distributions of the test statistic q for fits of...... κAZZ (κHZZ=0) ... κHZZ (κAZZ=0) κSM · cosα=1
Regions
excluded
at 95% CL
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Introduction Study of the Tensor Structure of Higgs Boson Couplings Summary
Summary
Measurement of the anomalous couplings :
– More events observed in each category then expected
– Too low statistic to observe a significant deviation from the SM predication
– Excluded regions at 95% confidence level:
κAgg < -0.68 and κAgg > 0.68κAZZ < -5.2 and κAZZ > 5.2κHZZ < 0.8 and κHZZ > 4.5
Outlook: Combine event yield and angular distribution information
1. non-SM coupling to gluons 2. non-SM coupling to vector bosons
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings 14/14
BACKUP
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings
Full Categorization
ttH-like
118 GeV < m4l < 129 GeV
≥ 1 extra leptons
≥ 2 Jets
= 0 Jet
= 1 Jet
mJJ > 120 GeV
mJJ < 120 GeV
60 GeV < pT 4l < 120 GeV
pT 4l > 120 GeV
pT 4l < 60 GeV
ggF-enrichedVBF-enrichedVH-enrichedttH-enriched
PT 4l > 150 GeV
PT 4l < 150 GeV
PT j1 > 200 GeV
PT j1 < 200 GeV
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 1
κSM free
Avvκ8− 6− 4− 2− 0 2 4 6 8
)λ-2
ln (
0
2
4
6
8
10
12
14
16
18
20
68% CL
95% CL
Observed
SM expected
ATLAS Internal 4l→ ZZ* →H
-113 TeV, 36.1 fb
freeSMκ = 1, Hggκ
= 1.2SMκ| = 1.5, AvvκObserved: | = 1.0SMκ = 0.0, AvvκExpected:
Hvvκ6− 4− 2− 0 2 4 6
)λ-2
ln (
0
5
10
15
20
25
30
68% CL
95% CL
Observed
SM expected
ATLAS Internal 4l→ ZZ* →H
-113 TeV, 36.1 fb
freeSMκ = 1, Hggκ
= 1.2SMκ = 2.2, HvvκObserved: = 1.0SMκ = 0.0, HvvκExpected:
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 2
2D scans
Avvκ6− 4− 2− 0 2 4 6
SMκ
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
Best FitObserved 95% CL
SM
SM expected 95% CL
ATLAS Internal 4l→ ZZ* →H
-113 TeV, 36.1 fb
= 0Hvvκ = 1, Hggκ
= 1.2SMκ| = 1.5, AvvκObserved: | = 1.0SMκ = 0.0, AvvκExpected:
Hvvκ6− 4− 2− 0 2 4 6
SMκ
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
Best FitObserved 95% CL
SM
SM expected 95% CL
ATLAS Internal 4l→ ZZ* →H
-113 TeV, 36.1 fb
= 0Avvκ = 1, Hggκ
= 1.2SMκ = 2.1, HvvκObserved: = 1.0SMκ = 0.0, HvvκExpected:
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 3
2D scans
Avvκ6− 4− 2− 0 2 4 6
Hvv
κ
4−
2−
0
2
4
6
8
10
12
14
Best FitObserved 95% CL
SM
SM expected 95% CL
ATLAS Internal 4l→ ZZ* →H
-113 TeV, 36.1 fb
= 1SMκ = 1, Hggκ
= 2.9Hvvκ| = 0.5, AvvκObserved: | = 0.0Hvvκ = 0.0, AvvκExpected:
Avvκ6− 4− 2− 0 2 4 6
Hvv
κ
4−
2−
0
2
4
6
8
10
12
14
Best FitObserved 95% CL
SM
SM expected 95% CL
ATLAS Internal 4l→ ZZ* →H
-113 TeV, 36.1 fb
freeSMκ = 1, Hggκ
= 1.7SMκ = 2.1, Hvvκ| = 0.3, AvvκObserved: | = 1.0SMκ = 0.0, Hvvκ = 0.0, AvvκExpected:
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 4
SM Higgs Boson Production Cross Section
[TeV] s6 7 8 9 10 11 12 13 14 15
H+
X)
[pb]
→(p
p σ
2−10
1−10
1
10
210 M(H)= 125 GeV
LH
C H
IGG
S X
S W
G 2
016
H (N3LO QCD + NLO EW)
→pp
qqH (NNLO QCD + NLO EW)
→pp
WH (NNLO QCD + NLO EW)
→pp
ZH (NNLO QCD + NLO EW)
→pp
ttH (NLO QCD + NLO EW)
→pp
bbH (NNLO QCD in 5FS, NLO QCD in 4FS)
→pp
tH (NLO QCD, t-ch + s-ch)
→pp
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 5
CP-Violation in the 2HDM
Additional SU(2) doublet→ two neutral scalars (h,H), a pseudoscalar (A), two charged (H±)
2HDM potential:
V =1
2λ1(ϕ†1ϕ1
)2+
1
2λ2(ϕ†2ϕ2
)2+ λ3
(ϕ†1ϕ1
)(ϕ†2ϕ2
)+ λ4
(ϕ†1ϕ2
)(ϕ†2ϕ1
)+
1
2
[λ5(ϕ†1ϕ2
)2+ h.c.
]+
{[λ6(ϕ†1ϕ1
)2+ λ7
(ϕ†2ϕ2
)2] (ϕ†1ϕ2
)+ h.c.
}−{m211
(ϕ†1ϕ1
)+[m212
(ϕ†1ϕ2
)+ h.c.
]+ m2
22
(ϕ†2ϕ2
)}
no CP violation in the Higgs sector and no FCNC if:λ6 = λ7 = m2
12 = 0 (Z2 Symmetry)
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 6
CP-Violation in the 2HDM
Simplest case of CP violation in the Higgs sector:λ6 = λ7 = 0 and m2
12 = 0Parametrization of the minimum of the potential:
ϕ1 =
(0
1√2v1
), ϕ2 =
(0
1√2v2eiξ
)Relation: Im
(m2
12eiξ)=Im(λ5e2iξ
)v1v2
rephasing invariance⇒ ξ = 0
Mass squared matrix of the neutral sector:
M2 =
M211 M2
12 − 12 Imλ5v2 sinβ
M212 M2
22 − 12 Imλ5v2 cosβ
− 12 Imλ5v2 sinβ − 1
2 Imλ5v2 cosβ M233
λ5 = 0: three neutral Higgs state mix⇒ CP-violation
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 7
Backup
H → ZZ∗ → 4µ
µ µ
µ µ
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 8
H → ZZ∗ → 4ℓ Event Selection
2 pairs opposite electric charge,same flavourCut on invariant masses:
– Leading lepton pair:50 GeV < m12 < 106 GeV
– Off-shell Z: mthreshold < m34 < 115 GeV
Muon (electron) isolation:Trackisolation:Itrackµ(e) =
(∑ptrackT
)/pℓT(E
ℓT) < 0.15 (0.15)
Calorimeterisolation:Icaloµ(e) =
(∑EclusterT
)/pℓT(E
ℓT) < 0.30 (0.20)
d0-significance:Muons: |d0/σd0 | < 3.0Electrons: |d0/σd0 | < 5.0
ℓ ℓ
ℓ ℓ
Higgs-Signal,ZZ∗
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 9
H → ZZ∗ → 4ℓ Event Selection
2 pairs opposite electric charge,same flavourCut on invariant masses:
– Leading lepton pair:50 GeV < m12 < 106 GeV
– Off-shell Z: mthreshold < m34 < 115 GeV
Muon (electron) isolation:– Track-based isolation:
Itrackµ(e) =(∑
ptrackT
)/pℓT(E
ℓT) < 0.15 (0.15)
– Calorimeter-based isolation:Icaloµ(e) =
(∑EclusterT
)/pℓT(E
ℓT) < 0.30 (0.20)
d0-significance:– Muons: |d0/σd0 | < 3.0– Electrons: |d0/σd0 | < 5.0
ℓ ℓ
ℓ ℓ
Higgs-Signal,ZZ∗
ℓℓ
ℓ ℓ
Z+ bbb
b
y
x
d0
trackPrimaryVertex
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 9
Branching Ratios of the SM Higgs Boson
[GeV]HM120 122 124 126 128 130
Bra
nchi
ng R
atio
-410
-310
-210
-110
1
LH
C H
IGG
S X
S W
G 2
016
bb
ττ
µµ
cc
gg
γγ
ZZ
WW
γZ
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 10
pp Collision Data Recorded with the ATLAS Detector
Number of expected pp collisions:
Nexp =L · σ =
∫dt L · σ
L ∝ nb · N2b · frev
Run I (2011+2012):–
√s = 7 TeV: L= 4.6 fb−1
–√s = 8 TeV: L= 20.7 fb−1
Run II (since 2015):–
√s = 13 TeV: L= 36.1 fb−1
Delivered luminosity:
Month in YearJan Apr Jul
Oct
]1
De
live
red
Lu
min
osity [
fb
0
5
10
15
20
25
30
35
40
45
ATLAS Online Luminosity
= 7 TeVs2011 pp
= 8 TeVs2012 pp
= 13 TeVs2015 pp
= 13 TeVs2016 pp
2/1
7 c
alib
ratio
n
This study:Run II pp collision data L= 36.1 fb−1
2016
2012
20112015
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Production and Decay of the SM Higgs Boson at the LHC
Production of the SM Higgs boson with a mass of 125 GeV at√s=13 TeV:
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
HW/Z
q
q
W/Z
H
g
g
t/b
t/b
H
Decay of the SM Higgs boson:
H
f
f
H
Z∗/W ∗
Z/W
t/b/W+
t/b/W
t/b/W−
H
γ
γ
t
t
t
H
g
g
ggF VBF VH ttHbbH
H → VV
87.4% 6.8% 4.0% 1.8%
66% 24%
0.0124%
0.2% 9%
H → ff H →γγ H → gg
H → ZZ∗ → 4ℓ
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 12
Full Event Selection
Table:Event selection criteria applied in the H → ZZ∗ → 4ℓ analysis [?].
Lepton Requirements
ElectronsET > 7 GeV and |η| < 2.47z0 · sin(θ) < 5 mm
Muons
pT > 5 GeV and |η| < 2.7pT > 15 GeV and |η| < 0.1 (CT muons)z0 · sin(θ) < 5 mm|d0| < 1 mm
Event selection
Higgs Boson Candidate
Two lepton pairs of same-flavour and opposite-chargepT > 20, 15, 10 GeV for the three highest-pT leptons∆R(ℓ, ℓ′) > 0.10 (0.20) for same- (different-) flavour leptonsmℓℓ > 5 GeV for same-flavour opposite-charge di-lepton pairs50 GeV< m12 < 106 GeVmthreshold < m12 < 115 GeV
Lepton Isolation
Muon track isolation (∆R ≤ 0.3): Itrackµ < 0.15
Muon calorimeter isolation (∆R = 0.2): Icaloµ < 0.30
Electron track isolation (∆R ≤ 0.2): Itracke < 0.15
Electron calorimeter isolation (∆R = 0.2): Icaloe < 0.20|d0/σd0 | < 3(5) for muons (electrons)
Vertex Selectionχ2/Ndof < 6 for 4µ candidatesχ2/Ndof < 9 for 2e2µ, 2µ2e, 4e candidates
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 13
The H → ZZ → 4ℓ Decay ChannelSignal:
Z∗
Z
H
`+
`−
`+
`−
Irreducible background:
Z/γ
Z/γ
`+
`−
`+
`−
q′
q
Reducible background: at least one lepton originates from a gluon or jet
Z
g
`+
`−
q
qq′
q
b
g
t
t
W−
bW+
`−
ν`
`+
ν`
g
g
ℓ± = e±,µ±
ZZ∗
Estimated with Monte Carlo Simulation
Data driven estimation
tt
Z+ jets
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 14
Results of the Event Selection
Invariant mass spectrum after event selection:
Good agreement between dataand simulation
Observed and expected numberof events in118 GeV < m4ℓ < 129 GeV:
Signal 54.0 ± 4.0ZZ∗ 19.7 ± 1.5Z+jets, tt 3.9 ± 0.5
Total Expected 77.0 ± 4.0Total Observed 95.0 [GeV]Constrained
4lm
80 100 120 140 160
Events
/2.5
GeV
0
10
20
30
40
50
60 Data
= 125.09 GeV)H
(mHiggs
ZZ*
+V, VVV tt
tZ+jets, t
Uncertainty
ATLAS Preliminary
4l→ ZZ* →H 113 TeV, 36.1 fb
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 15
CP measurements in the H → ZZ∗ → 4ℓ channelEffective field theory (EFT) implemented in the so called Higgscharacterisation model (arXiv:1306.6464)
LV0 =
{cακSM
[1
2gHZZZµZµ + gHWWW+
µW−µ
]−
1
4
[cακHγγgHγγAµνAµν + sακAγγgAγγAµν Aµν
]−
1
2
[cακHZγgHZγZµνAµν + sακAZγgAZγZµν Aµν
]−
1
4
[cακHgggHggGa
µνGa,µν + sακAgggAggGa
µν Ga,µν]
−1
4
1
Λ
[cακHZZZµνZµν + sακAZZZµν Zµν
]−
1
2
1
Λ
[cακHWWW+
µνW−µν + sακAWWW+
µνW−µν
]−
1
Λcα[κH∂γZν∂µA
µν + κH∂ZZν∂µZµν + κH∂W(W
+ν ∂µW
−µν + h.c.)] }
X0
Lf0 =−
∑f=t,b,τ
ψf (cακHffgHff + i sin (α)κAffgAffγ5)ψfX0
CP violation: Mixture of CP even and CP odd
Bosons
Fermions
Done in Run 1SM CP-even,tree-level
BSM CP-evenBSM CP-oddα = CP mixing angle
κ = HC coupling parameter
g = coupling strength SM or MSSM
Λ = cut-off energy
cα = cos (α)
sα = sin (α)
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 16
Measurement of the HVV Tensor Coupling
CP-sensitive kinematic discriminants in the decay system :
z′
z
Φ1
Φ
p X
Z2
Z1
p
µ+
µ−
θ1
θ∗
θ2
e+
e−
m12, m34, cos(θ1), cos(θ2), ϕ, ϕ1, θ∗ )1θcos(1− 0.5− 0 0.5 1
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ries
/ 0.2
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2
4
6
8
10
12
14
16
18 ATLAS
4l→ZZ*→H-1 = 7 TeV, 4.5 fbs
-1 = 8 TeV, 20.3 fbs
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Information from kinematicdistributions (used in Run-1)
∢(Z1, ℓ−)
Eur. Phys. J. C75 (2015) 476
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 17
Signal Modelling via Morphing Method
Number of input samples Ti is dependent on the number of couplings onewants to model
N =np (np + 1)
2· nd (nd + 1)
2+
(4 + ns − 1
4
)+
(np · ns +
ns (ns + 1)
2
)· nd (nd + 1)
2+
(nd · ns +
ns (ns + 1)
2
)· np (np + 1)
2
+ns (ns + 1)
2· np · nd + (np + nd)
(3 + ns − 1
3
)
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 18
Relevant couplings in ggF/VBF production in H4ℓ channel
Production: ggF,VBF
t/b
g
g
H
W/Z
W/Z
q′
q
q′
q
H
Decay: H → 4ℓ
Z∗
Z
H
`+
`−
`+
`−κHgg
κAgg
κSM,κHzz, κHww, κHzγ ,κHγγ , κH∂z,
κH∂w, κH∂γ
κAzz, κAww,
κAγγ , κAzγ ,
κSM
κAzz, κAγγ , κAzγ ,
κHzz, κHγγ , κHzγ ,κH∂z, κH∂γ
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 19
Signal Modelling via Morphing MethodStatistical uncertainty of output distribution:
∆Tbinout =
√√√√∑i
wi (κout; κi)NbinMC,i (κi) ·
(σi(κi)LNMC,i(κi)
)2
SMκ
BS
Mκ
Validation Point
B1 B2
B3
A1
A2 A3
Observable sensitive to anomalous coupling
Num
ber
of e
xpec
ted
even
ts
Validation sampleMorphing output set AMorphing output set B
Different choice of input samples⇒ different statistical uncertaintiesIn addition, require that predicted value of the observable agrees withvalidation value
fixed κ
Set of input samples:◦ A1, ◦ A2,◦ A3• B1, • B2,• B3
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 20
Set of Input Samples for Modelling VBF and VH productionVBF and VH production have the same coupling structure:
W/Z
W/Z
q′
q
q′
q
HW/Z
q
q
W/Z
H
⇒ VBF and VH production are combinedAssumption: κXZZ = κXWW, where X = H,ASeparate model for κAZZ and κHZZ
VBF VHκHZZ, κAZZκSM
κHZZ, κAZZ κSM
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 21
Set of Input Samples for Modelling VBF and VH production
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
Production mode np nd ns N
VBF+VH 0 0 2 5
Azzκ15− 10− 5− 0 5 10 15
Hzz
κ
10−
5−
0
5
10
V_kHVV5_kSM1
V_kHVV2p5_kSM1
V_kHVVm5_kSM1
V_kHVVm2p5_kSM1
V_kAVV5_kSM1
V_kAVV2p5_kSM1
V_kAvvm5_kSM1
V_kAVVm2p5_kSM1
V_kSM1
V_kAVV15_kSM0
V_kHVV10_kSM0
=1SM
input samples, g
=0SM
input samples, g
=1SM
validation samples, g
κSMκHZZ or κAZZ
κSMκHZZ or κAZZ
H → ZZ∗ → 4ℓ
VBF
Input samples in κAZZ-κHZZ plane:
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 22
Set of Input Samples for Modelling VBF and VH production
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
Production mode np nd ns N
VBF+VH 0 0 2 5
12m
50 55 60 65 70 75 80 85 90 95 100
cros
s se
ctio
n in
[pb]
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
V_kAVVm2p5_kSM1, validation sample
V_kAVVm2p5_kSM1, signal model
= 13 TeVs4l, →ZZ→MadGraph5_aMC@NLO, VBF: H
κSMκHZZ or κAZZ
κSMκHZZ or κAZZ
H → ZZ∗ → 4ℓ
VBF
Validation of the input sample set: κAZZ
Good agreement between predic-tion and validation point
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 22
Set of Input Samples for Modelling VBF and VH production
W/Z
W/Z
q′
q
q′
q
H
Z∗
Z
H
`+
`−
`+
`−
Production mode np nd ns N
VBF+VH 0 0 2 5
12m
50 55 60 65 70 75 80 85 90 95 100
cros
s se
ctio
n in
[pb]
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
V_HVVm2p5_kSM1, validation sample
V_HVVm2p5_kSM1, signal model
= 13 TeVs4l, →ZZ→MadGraph5_aMC@NLO, VBF: H
κSMκHZZ or κAZZ
κSMκHZZ or κAZZ
H → ZZ∗ → 4ℓ
VBF
Validation of the input sample set: κHZZ
Good agreement between predic-tion and validation point
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 22
CP sensitive discriminants in the decay system
Eur. Phys. J. C75 (2015) 476
[GeV]12m50 60 70 80 90 100 110
Ent
ries
/ 5 G
eV
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25ATLAS
4l→ZZ*→H-1 = 7 TeV, 4.5 fbs
-1 = 8 TeV, 20.3 fbs
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
[GeV]34m20 30 40 50 60 70
Ent
ries
/ 5 G
eV
0
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15
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25ATLAS
4l→ZZ*→H-1 = 7 TeV, 4.5 fbs
-1 = 8 TeV, 20.3 fbs
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
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CP sensitive discriminants in the decay system
Eur. Phys. J. C75 (2015) 476
)2θcos(1− 0.5− 0 0.5 1
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ries
/ 0.2
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25 ATLAS
4l→ZZ*→H-1 = 7 TeV, 4.5 fbs
-1 = 8 TeV, 20.3 fbs
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
φ3− 2− 1− 0 1 2 3
/4)
πE
ntrie
s / (
0
5
10
15
20
25 ATLAS
4l→ZZ*→H-1 = 7 TeV, 4.5 fbs
-1 = 8 TeV, 20.3 fbs
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
Data
Background ZZ*
tBackground Z+jets, t
SM+ = 0PJ- = 0PJ
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Signal Modelling via Morphing MethodContinuous signal model to describe signal expectation in dependence onBSM couplingsPredicts kinematic distributions and cross-sections at every parameter point
Tout(κout) =Ninput∑i=1
wi(κout; κi) · Tin(κi) κ = (κSM, κ1BSM, . . . , κ
nBSM)
Assumption:
T (κ) ∝ |M(κ)|2 =(∑
α∈p,s
καO(κα)
)2
︸ ︷︷ ︸production
·(∑
α∈d,s
καO(κα)
)2
︸ ︷︷ ︸decay
Challenge: Find the set of input samples which gives the lowest statisticaluncertainty
p: productiond: decays: shared in both
Output distribution weight Input distribution
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 25
Morphing: Calculation of weights functions
Tout(gout) =Ninput∑i=1
wi(gout; gi) · Tin(gi) e.g. T = σ · BR, T = cos θ1
Ansatz for morphing weights:
wi = (ai1gSM2 + ai2gBSM
2 + ai3gSMgBSM)
Requirement for calculation of constants:
wi = 1 and wj =i = 0 if gout = gi
⇒ Linear system of equations, solveable through matrix inversion
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 26
Morphing: Specific example
SM
Mix
BSM
Interferenceg2SM
g2BSM
+1
−1
−1
gSM · gBSM
(gSM,gBSM)
(1,0)
(1,1)
(0,1)
Morphing function for this specific example:Tout(gSM, gBSM) = (gSM2 − gSMgBSM)︸ ︷︷ ︸
=w1
Tin(1, 0)+(gBSM2 − gSMgBSM)︸ ︷︷ ︸=w2
Tin(0, 1)+gSMgBSM︸ ︷︷ ︸=w3
Tin(1, 1)
⇒ Set of input samples can be arbitrarily chosen as long as linear system ofequations can be solved
06/12/2017 V. Walbrecht - Study of the Tensor Structure of Higgs Boson Couplings B/U 27
Recommended