Higgs physics in ATLAS - CERNcds.cern.ch/record/2213438/files/ATL-PHYS-SLIDE-2016-576.pdfγγ 0.23...

Thibault Guillemin (LAPP), on behalf of the ATLAS collaboration

SEARCH 2016, Oxford

August 31-September 2, 2016

Higgs physics in ATLAS

Thibault Guillemin

The Run 1 and Run 2 Higgs datasets

2

Datasets analysed

2011: 5 fb-1, 7 TeV

2012: 20 fb-1, 8 TeV

2015: 3 fb-1, 13 TeV

2016: 10-12 fb-1, 13 TeV

Pileup in 2016 higher than in Run 1

Main ATLAS detector upgrade:

addition of an insertable B-layer (IBL)

4th pixel layer at 3.3 cm from the beam

Higgs physics in ATLAS, SEARCH 2016

Run 2

Outstanding performance

of the LHC in 2016

Run 2

Run 1

Run 1

Run 2

Thibault Guillemin

Outline

3

Overview of the Higgs main channels

Property measurement

BSM searches


Thibault Guillemin

Higgs channels

4

Channel BR (%)

bb 58.1

WW* 21.5

gg 8.18

ττ 6.25

cc 2.88

ZZ* 2.64

γγ 0.23

Zγ 0.15

μμ 0.022

Mass = 125.09 GeV

125 GeV is a reallly unique and fantastic place to study Higgs couplings…

CERN Yellow Report 4

The ‘big 5’ channels

currently accessible at LHC

Even more rare decays predicted in the SM

Ex: B.R.(H→J/Ψγ) = 2.8 10-6


Run 2 result

Run 1 result

(see backup)

Run 2 result

Run 2 result

Run 1 result

(see backup)

Run 2 result

Thibault Guillemin

H→γγ (1/3): analysis overview

5

Analysis key points

• Scaled photon pT thresholds:

0.35×mγγ and 0.25×mγγ

• Track-based and calorimeter-based

isolation criteria

• Neural network-based identification of

the vertex (exploiting in particular the pointing capabilities

of the electromagnetic calorimeter)

• Total background fitted directly on data (parameterization of the background model

determined from high statistics fast simulation

samples)

ATLAS-CONF-2016-067


γγ purity ~80%

Thibault Guillemin

H→γγ (2/3): fiducial and differential cross sections

6

Higgs mass fixed to the value of the combined ATLAS+CMS measurement: mH=125.09 GeV

(The fitted mass is compatible with this value within its statistical uncertainty.)

Differential cross sections

• mγγ fitted in each bin

• Unfolding method: bin-by-bin

Fiducial cross section: σfid (13 TeV) = 43.2 ± 14.9 (stat.) ± 4.9 (syst.) fb


Variables considered (distributions

split in 4 or 5 bins):

pTγγ, |yγγ|, |cos(θ*)|, njets, pT

j1, |ΔΦjj|, mjj

Slightly harder pT

spectrum in data

(as in Run 1)

SM: 62.8+3.4-4.4 fb

Thibault Guillemin

H→γγ (3/3): couplings

7

Reconstruction categories optimized to probe production modes

Sele

ction o

rder


• 13 reconstruction categories

• Predicted purity of the targeted

mode ~80%

Measured

Measured cross sections

Thibault Guillemin

H→ZZ*→4l (1/2): analysis overview

8

Analysis key points

• Low lepton pT thresholds: 7 GeV for

electrons and 5 GeV for muons

(τ decays not used)

• Channel with the highest S/B ratio:(main background from the non-resonant

ZZ* production)

S/B~2 in signal mass window

• Z-mass constraint applied (m4l resolution improved by 15%)

ATLAS-CONF-2016-079


Thibault Guillemin

H→ZZ*→4l (2/2): fiducial cross section and couplings

9

• Extraction of the fiducial cross section from an unbinned fit of m4l in

the range 115 < m < 130 GeV

Fiducial cross section: σfid(13 TeV) = 4.54+1.02-0.90 fb SM: 3.07+0.21

-0.25 fb

• 5 reconstruction categories

• New w.r.t. the Run 1 categorization:

1-jet category

VBF sensitivity increased by 20%

Measured cross sections

SM


• Fiducial cross section also measured

separately for the same- and

opposite-flavour final states

Thibault Guillemin

H→bb (1/3): VH analysis overview

10

Analysis key points

• Analysis performed in 3 channels:

ZH→ννbb, WH→lνbb and ZH→llbb

• Exactly 2 b-tag jets required (2-jet and

3-jet categories defined)

• High missing ET cut for the 0-lepton

selection (150 GeV)

• High pT,V selection: pT,V > 150 GeV (for the 2-lepton selection, 0-150 GeV region

also considered)

• Simultaneous fit to the BDT distributions

in 8 categories

ATLAS-CONF-2016-091


Thibault Guillemin

H→bb (2/3): VBF+γ analysis overview

11

Analysis key points

• H→bb VBF analysis (not in association

with a photon) performed in Run 1

(sensitivity ~5 times the SM)

• Topological 4-jet+γ trigger signature

implemented at Level-1 for Run 2

• Gluon-induced component of the

dominant non-resonant bbjjγ suppressed

• BDT against the non-resonant

background: mbb fits in 3 BDT regions

ATLAS-CONF-2016-063


BackgroundSignal

Thibault Guillemin

H→bb (3/3): couplings

12

μ = 0.21 ±0.36(stat.) ±0.36(syst.)

Run 1: μ = 0.52 ±0.32(stat.) ±0.24(syst.)

VBF+γ

Obs. (exp.) significance:

0.4 σ (1.9 σ)


VH


1.4 σ (2.6 σ)

Thibault Guillemin

ttH (1/2): analysis overview

13

Analysis key points

• Production mode probed in 3 channels:

bb, ‘multileptons’ and γγ

• ttH(bb)

- Many jets produced in the final state

- Modeling of tt+heavy flavour jets crucial

- HThad or MVA discriminants, depending on

the categories

• ttH(multileptons)

- 4 channels: same sign ee/μμ/eμ

with/without an extra τ, 3l and 4l

- Contributions from H→WW*, H→ττ and

H→ZZ*

- Fit to the data yields of all the categories

ATLAS-CONF-2016-080


ATLAS-CONF-2016-058

Thibault Guillemin

ttH (2/2): couplings

14


2.8 σ (1.8 σ)


ATLAS-CONF-2016-068

Run 1


2.3 σ (1.5 σ)

Thibault Guillemin

H→μμ

15

• Huge Drell-Yan background

• Analysis performed in categories:

central/non-central, low/medium/high pT,μμ, VBF

Most sensitive category

Very small branching ratio predicted in the SM: 0.02%

Coupling to the second generation of fermions


ATLAS-CONF-2016-041

Limit only ~4

times the SM!

Thibault Guillemin

Outline

16



BSM searches


Thibault Guillemin

Profiling the Higgs

17

• Large interplay between the various areas:

mass needed for predictions, constraints on different operators in an EFT

approach, simplified template cross sections under discussion,…

• Accuracy (prediction and measurement) is key to probe BSM effects.

Mass

Width and off-

shell couplingsSpin CP

CouplingsDifferential

cross sections

Higgs

measurements


(see backup)

Thibault Guillemin

Higgs mass

18

Precise Higgs mass measurement required for accurate predictions of

Higgs production and decay rates

Phys. Rev. D. 90,

052004 (2014)

Combined mass measurement in the H→γγ and H→ZZ*→4l channels


mH = 125.36 ±0.37(stat.) ±0.18(syst.) GeV

ATLAS+CMS Run 1 legacy combined measurement:

mH = 125.09 ±0.21(stat.) ±0.11(syst.) GeV

Phys. Rev. Lett. 114, 191803

Thibault Guillemin

Higgs width

19

Assuming no running of the effective couplings κg and κV and :

ΓHiggs < 23 MeV

• Direct limits at the GeV level

• Under some assumptions, the measurement of the off-shell signal strength

allows to set indirect constraints on the width. 3 channels considered: ZZ*→4l, ZZ*→2l2ν, WW*→2l2ν Eur. Phys. J. C.

(2015) 75:335

For mH = 125 GeV: ΓH = 4.1 MeV

μoff-shell < 5.5


1)(

)(**

VV

H

gg

VV

BB

HmK

mKR

μoff-shell=10

Large negative interference

with gg→VV background

Thibault Guillemin

Spin-CP from the diboson channels

20

1) Fixed spin-CP hypothesis tests: performed in the γγ, ZZ* and WW* channels

EPJC 75 (2015) 476

ZZ*: full kinematic

information available

γγ: cos(θ*) WW*: several spin-sensitive

kinematic variables

Several alternative spin and parity models

considered, including non-SM spin-0 and

spin-2 models with universal and non-

universal couplings to quarks and gluons:

exclusion of all hypotheses at 99.9% CL


2) Spin-CP mixing studies (see backup)

Thibault Guillemin

Couplings: Run 1 results

21

Production and decay signal strengths:

Combination:

Production mode signal strengths

(assuming SM BR’s)

Decay mode signal strengths

(assuming SM σ’s)

(assuming one common μ = μi×μf

for all processes)

μ = 1.18 ±0.10(stat.) ±0.07(syst.) ±0.08(th.)

Eur. Phys. J.

C76 (2016) 6


Thibault Guillemin

Interpretation: the κ-framework

22

To go beyond signal strength measurements, assumptions are needed.

• Only one single narrow resonance (zero-width

approximation)

• Only modifications of coupling strengths:

tensor structure of the SM

The goal is to test the compatibility of the SM

prediction with the data.

Processes with loops: effective couplings expressed as functions of the fundamental modifiers

For all channels:

Gluon fusion γγ decay

Coupling modifiers :

Various benchmark models tested, applying further assumptions


Computed using the best

available predictions

Thibault Guillemin

Example 1: couplings to bosons and fermions

23

Model to test the gauge versus Yukawa couplings

• No new particles in the loop

• No BSM decay

• Common modifiers for vector bosons and

for fermions

2-parameter fit

Sensitivity only to the sign of κV×κF (through interference terms in H→γγ, tH,

gg →ZH): κV≥0 assumed

Strongest constraint from H→WW* Negative relative sign disfavored at 4.0 σ


κV = κW = κZ

κF = κt = κb = κτ = κg = κμ

Thibault Guillemin

Example 2: coupling ratios

24

9-parameter fit

Custodial

symmetry

New charged

particles

New coloured

particles

Everything well compatible with the SM

Only ratios of coupling strengths can be measured at the LHC

without any assumption on the Higgs total width.

• New particles in loops allowed


Thibault Guillemin

Couplings: first Run 2 combination

25

ATLAS-CONF-2016-081

First Run 2 combination, based on H→ZZ* and H→γγ results

Production mode signal strengths

(assuming SM BR’s)

Global signal strength: μ = 1.13±0.18

Total cross section (extrapolated

from the fiducial measurements)

Combination performed for four different fit models based on event categorisation

and the number of measured parameters in each fit model (from 1 to 7)


Thibault Guillemin

Outline

26



BSM searches


Thibault Guillemin 27

What is BSM physics in the Higgs sector?

There are many ways to look for BSM physics in the Higgs sector...

Neutral heavy Higgs

BSM

Higgs

searches

Charged Higgs

Di-Higgs productionHiggs exotic

decays

Higgs lepton flavor

violating decays

BSM constraints from

coupling measurements

Higgs in decay

chains

Higgs as a portal

to hidden sectors

In the next slides:

1. More Higgs bosons

2. Di-Higgs production

3. Higgs BSM decays


Thibault Guillemin

More Higgs bosons

28

1. General heavy Higgs H

• H → ZZ or WW (see backup)

• H→Zγ→llγ (see backup)

• H→h+χχ (see backup)

• H→γγ

2. Charged Higgs H± in the 2HDM

• H+→τν

• H+→tb

3. Neutral Higgs A/H in the 2HDM

• A/H→ττ

• A/H→tt (Run 1)

A large number of searches for more Higgs bosons already performed at 13 TeV

In addition: BSM constraints from couplings (Run 1) (see backup)


Two-Higgs-doublet model:

- 4 types of model

- 5 physical bosons: h, H, A, H±

MSSM: special case of type II 2HDM

Thibault Guillemin

Heavy Higgs: H→γγ

29

Maximum significance: 3.9 σ,

for mH=750 GeV, ΓH=6%

2015 dataset JHEP08(2016)128

Limits set on

the combined

dataset


2016 dataset

No excess…

ATLAS-CONF-2016-059

Thibault Guillemin

Charged Higgs: H+→τν

30

• Production in association with a top quark

(dominant production mode for mH+>mt)

• Hadronic τ-decay

• ETmiss trigger (90 GeV threshold)

• Discriminant variable:

ATLAS-CONF-2016-088


Thibault Guillemin

Charged Higgs: H+→tb

31Higgs physics in ATLAS, SEARCH 2016

ATLAS-CONF-2016-089

• Production in association with a top quark

• Large b-tag jet multiplicity for signal

SR: 5j3b, 5j4b, ≥6j-3b and ≥6j-≥4b

• Discriminant: BDTs in the SR

• HThad used in the CR, included in a

simultaneous fit with the SR

CR SR

Thibault Guillemin

Neutral Higgs: A/H→ττ

32

• Production through gluon fusion or in

association with b quarks

• τ-decays considered: hh and lh channels

• b-tag and b-veto categories

• Discriminant variable:

ATLAS-CONF-2016-085


Gluon fusion b-associated

production

Thibault Guillemin

Neutral Higgs: A/H→tt


ATLAS-CONF-2016-073

Type II 2HDM

(μ=1):

tan(β)<0.85

excluded, for

mA=500 GeV

• Re-interpretation of a previous tt resonance

search

• Signal shape distorted due to the

interference with the tt background

Peak-dip structure

• Parameter of interest: signal strength μ

mtt parametrized as:

Thibault Guillemin

Di-Higgs production (1/3): 4b

34

• Resolved and boosted (large-R jets)

categories

• Requirement on the masses:

Limit ~30 times σSM

For H125:

σ(pp→hh)<1.0 pb

SM: σ = 33 fb

All di-Higgs searches performed in

the non-resonant and resonant cases

ATLAS-CONF-2016-049


• Discriminant: mhh

Thibault Guillemin

Di-Higgs production (2/3): WWγγ

35

• 2 photons, 2 jets (no b-jet), 1 lepton,

no ETmiss cut

• 0-lepton region: data-driven estimate

of the continuum background

• Counting experiment


For H125:

σ(pp→hh)<25 pb (13 pb)

SM: σ = 33 fb

ATLAS-CONF-2016-071


Limits decrease because of the increase of

the resonant production efficiency.

Thibault Guillemin

Di-Higgs production (3/3): bbγγ

36

Modest Run 1 excess (2.4 σ)

not confirmed

• 2 photons and 2 b-tag jets required

• 0-tag region: background efficiency

(resonant case) and data-driven

estimate of the continuum

background (non-resonant case)

ATLAS-CONF-2016-004


For H125:

σ(pp→hh)<3.9 pb (5.4 pb)

SM: σ = 34.2 fb


Thibault Guillemin

Higgs BSM decays

37

Only one result at 13 TeV

1. Exotic decays

• W(H→aa→4b)

2. Lepton flavor violating decays (Run 1)

• H→eτ/μτ (see backup)

3. Invisible decays (Run 1)

• Direct and indirect constraints (see backup)

• Dark matter portal (see backup)


Thibault Guillemin

W(H→aa→4b)


arXiv:1606.08391

Higgs decay in two light pseudo-scalars

predicted in several models, e.g. NMSSM

nb-jet njet

Limits set on σWH×BR(H→2a)×BR(a →2b)2

SR

• Search performed in the WH channel,

with W→lν (l = μ or e)

• Discriminant: BDTs in the SR

• ma mass range: 20-60 GeV

Thibault Guillemin

Towards Run 3 and beyond…

39

• Datasets:

- Run 2 (2015-2018): 100 fb-1

- Run 3 (2021-2023): 300 fb-1

- HL-LHC (2026-2035): 3000 fb-1

Challenging…

HH→bbbb, ttHH→ttbbbb also under study

Critical: b-tagging performance at <μ>=140

~Today’s

accura

cy

And many more things…

ATL-PHYS-PUB-2015-046

AT

L-P

HY

S-P

UB

-2014-0

16

λHHH measurement

Higgs precision program

HH→bbγγ HH→bbττ

ATL-PHYS-PUB-2014-019

Hashed areas: theory

Sensitivity to λSM1.3 σ 0.6 σ


Thibault Guillemin

Summary

40

Four years after the Higgs discovery, all measurements performed so far

are perfectly consistent with the SM predictions.

Thanks to the outstanding performance of the LHC, many Run 2 results

are already exceeding the Run 1 results.

We already have ~10 fb-1 of post-ICHEP data to analyse!

Huge and diverse program of Higgs physics (precision measurements and

direct searches) for Run 2, Run 3 and beyond: the exploration of the

scalar sector of the SM is only starting…


Thibault Guillemin

Backup

41

Thibault Guillemin

Higgs production at the LHC

42

Mode 8 TeV 13 TeV

ggF 21.4 48.5

VBF 1.60 3.78

WH 0.70 1.37

ZH 0.42 0.94

ttH 0.13 0.51

tH 0.020 0.077

bbH 0.20 0.49

Total 24.5 55.7

σ (pb), for mH = 125.09 GeV

Four main production mechanisms

ggF: 87%

VBF: 7%ttH: 0.9%

VH: 5%


Computations at NLO, NNLO or N3LO (ggF) in QCD

CERN Yellow

Report 4

Thibault Guillemin

H→WW*→lνlν: analysis overview (1/2)

43

Phys. Rev. D 92, 012006 (2015)


×10

Analysis key points

• Most abundant source of exploitable

Higgs decays

• Analysis performed in the μμ/ee/μe channels

• Not possible to fully reconstruct the invariant

mass of the final state: mT used

• Large tt background in 1- and 2-jet categories

(jet veto needed for ggF sensitivity)

• Small opening angle between the charged

leptons (V − A decay of the W bosons)

Thibault Guillemin

H→WW*→lνlν: couplings (2/2)

44

7 reconstruction categories

μ = 1.09 ±0.16(stat.) ±0.17(syst.)


Thibault Guillemin

H→ττ (1/2): analysis overview

45

Analysis key points

• Analysis performed in 3 channels:

ll (12%), lh (46%), hh (42%)

• Channels split in VBF and Boosted

categories

• ‘Embedding’ technique used for the

simulation of Z→ττ

• Kinematic fit of di-tau mass (Missing

Mass Calculator)

• Large sensitivity improvements with MVA

discriminants

JHEP 04 (2015) 117


Thibault Guillemin

H→ττ (2/2): couplings

46

μ = 1.43 ±0.27(stat.)±0.43(syst.)


4.5 σ (3.4 σ)


Phys. Rev. D 93, 092005 (2016)

VH channels also exploited

Thibault Guillemin

Simplified template cross section framework

47

arXiv:1605.04692

Stage-0

|yH| < 2.5


H→γγ measurement

Thibault Guillemin

Higgs width

48

Assuming no running of the effective couplings κg and κV and RH*B =1:

ΓHiggs < 23 MeV

Under some assumptions, the measurement of

the off-shell signal strength allows to set indirect

constraints on the width. 3 channels considered: ZZ*→4l, ZZ*→2l2ν, WW*→2l2ν

Eur. Phys. J. C.

(2015) 75:335

For mH=125 GeV: ΓH=4.1 MeV

Direct constraints : ZZ*: 2.6 GeV, γγ: 5.6 GeVPhys. Rev. D. 90,

052004 (2014)

- Large negative

interference with gg→VV

background

- Relative background

k-factor unknown:μoff-shell<5.5


Large theory progress

recently (see backup)

SMHH

shellonVshellong

shellon

shelloffVshelloffgshelloff sss

,

,2

,2

,2

,2

/

)ˆ()ˆ()ˆ(

)(

)(**

VV

H

gg

VV

BB

HmK

mKR

μoff-shell=10

Thibault Guillemin

Higgs off-shell effects at NLO


Thibault Guillemin

CP-mixing from the diboson channels

50

- EFT approach (Higgs boson characterisation model), valid up to Λ (1 TeV)

- BSM terms in the lagrangian describing the HVV vertex of the spin-0 resonance

Mixture of CP-even and CP-odd states?

κSM: SM

κHVV: BSM CP-even state

κAVV: BSM CP-odd state

Assuming:

- similar couplings to

Z and W

- only one component

present in each case


Thibault Guillemin

CP-mixing at 13 TeV

51

Study of BSM κHVV and κAVV sin(α) in H→ZZ*→4l

Yields in VBF and VH categories sensitive to BSM interactions in the HZZ

vertex (no angular analysis)

Assumptions:

- κ cos(α) =1 (SM-like interaction fixed to the SM)

- For each scan:

i) CP-even state: cos(α) =1 κHVV

ii) CP-odd state: κAVV sin(α)


ATLAS-CONF-2016-079

- Agreement between κHVV = 0

and the observed value: 2.1 σ

- Agreement between

κAVV sin(α) = 0 and the

observed value: 1.8 σ

Thibault Guillemin

CP invariance in the ττ channel

52

No hint of CP violation here…

Direct test of CP invariance in Higgs boson

production via vector-boson fusionarXiv:1602.04516

Single parameter

Effective Lagrangian:As the various processes

cannot be distinguished

experimentally:

First ‘Optimal Observable’:

Matrix element for

VBF production:

= 0 for SM

(combines 7 variables describing the final state)


Thibault Guillemin

Differential cross sections at 8 TeV

53

• Combination of the differential measurements

in H→γγ and H→ZZ* at 8 TeV:

pT,H, yH, njets and pT,j1

• Comparison to state-of-the-art predictions


Phys. Rev. Lett. 115, 091801

Thibault Guillemin

Constraints from an effective lagrangian approach

54

Physics Letters B 753

(2016) 69-85

Effective lagrangian, using the Strongly Interacting Light Higgs (SILH) basis

Simultaneous fit to 5 differential distributions in the γγ channel

Improvement mainly for cHW (~15%) w.r.t using a single variable (thanks to the

induced shape changes in the kinematics of the VBF process)


Thibault Guillemin

Absolute couplings

55

Generic model with only SM particles

• No BSM contributions to loops

• No BSM decay

• No invisible or undetected decay

6-parameter fit


Thibault Guillemin

Heavy Higgs decaying to ZZ or WW


H→ZZ→4lH→ZZ→llqq H→ZZ→llνν

H→ZZ→ννqq H→WW→eνμν H→WW→lνqq

ggF and VBF production modes probed

ATLAS-CONF-2016-079

ATLAS-CONF-2016-082 ATLAS-CONF-2016-074 ATLAS-CONF-2016-062

ATLAS-CONF-2016-082

ATLAS-CONF-2016-056

Thibault Guillemin

Heavy Higgs: H→Zγ


ATLAS-CONF-2016-044

• Search performed in the Z→llγ

channel (l= μ or e)

• Mass range: 250-2400 GeV

Thibault Guillemin

Heavy Higgs: H→h+χχ


ATLAS-CONF-2016-087

• Heavy scalar model: H decay to h and

a pair of dark matter candidates χ

(mχ = 50 GeV and 60 GeV considered)

• Signal regions defined with ETmiss

significance and pTγγ requirements

• Mass range: 2mh < mH < 2mt

Thibault Guillemin

BSM constraints from couplings

59

JHEP11(2015)206

hMSSM

2HDM

Limits are set on parameters in extensions of the Standard Model.

Scale factors (κ) for the Higgs couplings are expressed as functions

of the model free parameters.

2 parameters: mA, tan(β)

6 parameters: mh, mH, mA, mH+/-, tan(β),

α (mixing angle between h and H)


Thibault Guillemin

H→Φγ

60

Limit ~600 times the SM

Decay predicted in the SM (BR = 2.3 10-6)

Decays to a light meson and a photon can be used to probe the Yukawa

couplings to light (u, d, s) quarks.

• Channel: Φ→K+K-

• Backgrounds: multijet and γ+jet

Run 1: searches performed in the H→J/Ψγ and Υ(ns)γ channels

arXiv:1607.03400


Thibault Guillemin

Lepton flavor violating decays

61

- Lepton-flavour-violating decays can occur naturally

in many BSM models…

- H→eμ decay (indirectly) tightly constrained from μ→eγ

measurements (MEG experiment): BR<10-8

• Search for H→eτ and H→μτ

• Analysis channels: e-τh, e-τμ, μ-τe

• Final discriminants

- τh: mMMC

- τl:

BR(H→eτ) < 1.04% (1.21%)

BR(H→μτ) < 1.43% (1.01%)

arXiv:1604.07730

CMS Run 1:

BR(H→μτ)=0.84%

(2.4 σ)


Thibault Guillemin

Dark matter portal

62

• WIMP taken to interact very weakly

with the SM particles, except for the

Higgs boson

• BRinv assumed to be fully coming from

the decay to WIMPs

BR depends on the spin of the WIMP

• Valid up to mWIMP<mH/2 (decay to 2

WIMPS)

Limits set on the cross section for scattering between the WIMP and nucleons via Higgs boson

exchange (form factor associated with the Higgs boson–nucleon coupling used as an input)

Significantly better limits at low mass (<10 GeV) for all assumptions

JHEP11(2015)206


Thibault Guillemin

Invisible decays: direct and indirect constraints

63

SM: BRinv = 0.1% (via H→ZZ*→4ν)

3 direct searches performed:

• ZH with Z→ll

• W/Z-H with W/Z→jj

• VBF (the most powerful channel)

VBF + ETmiss cuts

Assuming the SM production cross sections, limits set on BRinv

Limits

Channel Obs. Exp.

ZH 0.75 0.31

W/Z-H 0.78 0.62

VBF 0.28 0.86

Combined 0.25 0.27

Signal Background

JHEP11(2015)206Indirect constraints from the coupling fit,

combining all the visible decays channels

(some model dependency):

BRinv < 0.49 (0.48)

Direct and indirect combined:

BRinv < 0.23 (0.24)


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