higgs boson decays to light scalars at atlas · 2020. 10. 26. · atlas 2hdm+s h 125!aa summary...

h125

Jet

`+

`−

a

Z

Higgs Boson Decays to Light Scalars at ATLAS

University of Oxford, 20th October 2020

Elliot Reynolds

This project has received funding from the European Research Council (ERC) under the European Union’s

Horizon 2020 research and innovation programme under grant agreement no 714893 (ExclusiveHiggs)

Ways to Extend the HiggsSector

Standard Model Higgs Sector 128

Higgs Doublet field introduces gauge invariant mass terms to theStandard Model (SM), facilitates electroweak (EW) symmetry

breaking (EWSB), and preserves the unitarity of WLWL → WLWL

φ = 1√2

(0

v + h(x)

)φ = 1√

2

(φ1(x) + iφ2(x)φ3(x) + iφ4(x)

)→ mW = 1

2gW v

mZ = 12v√g2W + g ′2

Observed Higgs Boson 228

Single neutral Higgs boson (h125) with a mass of 125 GeVdiscovered in 2012 by ATLAS and CMS

arXiv:1307.1347

ATLAS-CONF-2018-031

https://arxiv.org/abs/1307.1347

http://cdsweb.cern.ch/record/2629412

Observed Higgs Boson 228

Single neutral Higgs boson (h125) with a mass of 125 GeVdiscovered in 2012 by ATLAS and CMS

arXiv:1307.1347 ATLAS-CONF-2018-031



Extended Higgs Sectors 328

The SM is not the only possible Higgs sector, just the simplest

More motivations: Supersymmetry, CP-violation, dark matter...

EW precision measurements impose:ρ ≡ m2

W /(m2Z cos2 θW ) = 1.00039± 0.00019

Naturally achieved by configuration of scalar singlets and doublets

Simplest extensions to the SM Higgs sector:

Higgs doublet with one or more additional scalar singletsTwo Higgs doublet model (2HDM)2HDM with an additional singlet (2HDM+S)

More complex scalar sectors (including involving triplets) are possible,leading to exotic signatures such as doubly charged Higgs bosons




http://pdg.lbl.gov/2019/reviews/rpp2019-rev-standard-model.pdf


Two Higgs Doublet Model 428

The 2HDM has a pair of scalar doublet fields

Physical Higgs bosons: h and H (CP-even), a (CP-odd), and H±

tanβ = v2/v1

To avoid tree-level flavour changing neutral currents, all fermions of agiven charge and quantum numbers couple to one doublet (arXiv:1207.1083)

2HDM Type First Doublet Second Doublet

Type-I All fermionsType-II (Supersymmetry) Up-type fermions Down-type fermions

Type-III Quarks LeptonsType-IV Up-type quarks Down-type quarks

Down-type leptons Up-type leptons


Two Higgs Doublet Model with an Additional Singlet 528

The 2HDM+S extends the 2HDM by one singlet field

2HDM scalar sector plus one neutral CP-even and one neutralCP-odd scalar

The Type-II 2HDM+S is featured in Supersymmetric models, where itsolves a naturalness problem in the Higgs mass scale


Type-II 2HDM+S BR(a→ SM) 628

1 2 5 10 20 5010-4

0.001

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arXiv:1312.4992


Heavy or Light? 728

The new scalars can be heavy...

Or they can be light

Many active search channels:

H → ττ (arXiv:2002.12223)H → µµ (arXiv:1901.08144)H →WW (arXiv:1710.01123)H → γγ (arXiv:1707.04147)bH → bbb (arXiv:1907.02749)H± → tb (arXiv:1808.03599)H± → τν (arXiv:1807.07915)H± → ZW (arXiv:1806.01532)H±± →W±W±

(arXiv:1808.01899)

They could be too heavy to beproduced at the LHC

Previous experiments would nothave discovered them if theironly large coupling is to h125

h125 → aa and h125 → Zapossible

Subject of what follows

Small natural width of h125means even small couplings tonew light resonances would leadto large BRs










Heavy or Light? 728

The new scalars can be heavy... Or they can be light

Many active search channels:

H → ττ (arXiv:2002.12223)H → µµ (arXiv:1901.08144)H →WW (arXiv:1710.01123)H → γγ (arXiv:1707.04147)bH → bbb (arXiv:1907.02749)H± → tb (arXiv:1808.03599)H± → τν (arXiv:1807.07915)H± → ZW (arXiv:1806.01532)H±± →W±W±

(arXiv:1808.01899)

They could be too heavy to beproduced at the LHC














Heavy or Light? 728

The new scalars can be heavy... Or they can be light

Γh125≈ 4.07 MeV

Γh125/mh125

≈ 3.3× 10−5

H → bb,ττ suppressed byyb,τ < O(10−2)

H → γγ,gg ,Zγ suppressed byloop factors

H → WW ∗,ZZ∗,tt̄ suppressed byphase space





Current ATLAS SearchProgramme

ATLAS Detector 828

LHC: 13 TeV pp collisions. Run 2: Lint = 139 fb−1 to date

arXiv:1011.6665


ATLAS 2HDM+S h125 → aa Summary Plots 928

tanβ

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=0.5

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1

arXiv: 1505.01609ττµµ → aa→HRun 1

arXiv: 1509.05051γγγγ → aa→HRun 1

arXiv: 1802.03388µµµµ → aa→HRun 2

arXiv: 1803.11145jjγγ → aa→HRun 2

arXiv: 1806.07355 bbbb→ aa→HRun 2

arXiv: 1807.00539µµ bb→ aa→HRun 2

σ 1 ±expected observed

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








ATL-PHYS-PUB-2018-045

Very few h125 → Za decays modes!BR(h125 → aa) = 100%h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµh125 → aa→ bbbbtanβ suppression of down-type lepton couplings!

h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµ

tanβ suppression of down-type quark couplings!

h125 → aa→ bbµµh125 → aa→ bbbb

tanβ suppression of down-type fermion couplings!

h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµh125 → aa→ bbbb

h125 → aa→ γγjj? h125 → aa→ γγγγ?h125 → aa→ γγjj? h125 → aa→ γγγγ?

1 2 5 10 20 5010-4

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a→ γγ



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=0.5

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!

BR(h125 → aa) = 100%h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµh125 → aa→ bbbbtanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

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5−10

4−10

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10

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→ B

(H×

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σHσ

95%

CL

on

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!

BR(h125 → aa) = 100%

h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµh125 → aa→ bbbbtanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

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5−10

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!BR(h125 → aa) = 100%

h125 → aa→ µµµµ

h125 → aa→ µµττh125 → aa→ bbµµh125 → aa→ bbbbtanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

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[GeV]am

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

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[GeV]am

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510

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(H×

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σHσ

95%

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ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

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1−10

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10

210

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→ B

(H×

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95%

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60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

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→ B

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-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!BR(h125 → aa) = 100%h125 → aa→ µµµµ

h125 → aa→ µµττ

h125 → aa→ bbµµh125 → aa→ bbbbtanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

6−10

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10

210

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510

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→ B

(H×

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σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

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95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

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on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

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810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

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810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SMσ

Hσ

95%

CL

on

60



-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!BR(h125 → aa) = 100%h125 → aa→ µµµµh125 → aa→ µµττ

h125 → aa→ bbµµ

h125 → aa→ bbbbtanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

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1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SMσ

Hσ

95%

CL

on

60



-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!BR(h125 → aa) = 100%h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµ

h125 → aa→ bbbb

tanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SMσ

Hσ

95%

CL

on

60



-1 = 8 TeV, 20.3 fbs: Run 1









Very few h125 → Za decays modes!BR(h125 → aa) = 100%h125 → aa→ µµµµh125 → aa→ µµττh125 → aa→ bbµµh125 → aa→ bbbb

tanβ suppression of down-type lepton couplings!







1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SMσ

Hσ

95%

CL

on

60



-1 = 8 TeV, 20.3 fbs: Run 1
















1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ



tanβ

=5

tanβ

=0.5

Type-II

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-III

1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

6−10

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410

510

610

710

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








Type-IV

1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SM

σHσ

95%

CL

on

60


ATLAS Preliminary

-1 = 13 TeV, 36.1 fbs: Run 2

-1 = 8 TeV, 20.3 fbs: Run 1








1 10

[GeV]am

3−10

2−10

1−10

1

10

210

310

410

510

610

710

810

aa)

→ B

(H×

SMσ

Hσ

95%

CL

on

60



-1 = 8 TeV, 20.3 fbs: Run 1















h125 → aa→ γγjj? h125 → aa→ γγγγ?

h125 → aa→ γγjj? h125 → aa→ γγγγ?

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=0.5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

1 2 5 10 20 5010-4

0.001

0.01

0.1

1

ma @GeVD

BrHa®SML

tan Β=5, TYPE II

bbccssΤΤΜΜgg

uuddΓΓ

a→ γγ


New Ideas Required! 1028

Very few searches for h125 → Za

Most searches for a use its decays to down-type fermions

Both gaps can be filled with a search for h125 → Za → ``j

Major challenge from overwhelming Z + jets background

New ideas required to address this...

h125→ Za→ ``jarXiv:2004.01678 and Auxiliary Material

https://arxiv.org/abs/2004.01678?fbclid=IwAR1z3Jl5WG9CSZnteYy4kj81_KrA1hZnLcfLjG7aX-Z-ykEiV-Ki8zY1jTM

https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HDBS-2018-37/?fbclid=IwAR1oDIYHvbnLVOA7YAnQdGvit04gAaXnyz8Xh1yJPB366zf5KRKl6H9hRGU

Aims and Motivation 1128

Aims

Use full ATLAS Run II dataset (139 fb−1)to perform first search forh125 → Z(`+`−)a/Q(had), ` = e or µ

Interpret resonance as J/ψ or ηc , or a(BSM) with ma <4 GeV

Charmonium Motivation

h125

Jet

`+

`−

a

Z

Higgs boson decays to Z + light resonances unconstrained

Potential constraints on Higgs boson coupling to charm-quark

BSM Motivation

Fills both gaps in the search programme: H → Za, anddecays of a other than to down-type fermions

Physics Processes and Simulation 1228

Physics Processes

Focus on low mass (< 4 GeV) a signals

Higher BR to light hadrons and unique decay kinematics

Signals from inclusive Higgs boson production

Dominant background: Z + jetsSmall contributions from tt̄ and diboson

Simulation

Signals modelled using Powheg, Pythia8 and EvtGen

Z + jets modelled using Sherpa 2.2.1

Full Geant4 simulation of the ATLAS detector

Event Selection 1328

Selection Details

Triggers Single lepton triggers pT, lead > 27 GeVLeptons N` ≥ 2 with pT > 18 GeVZ boson 2 SF OS leptons, with |mll −mZ | < 10 GeVJet (a) Anti-kT jet, radius parameter 0.4,

formed of calorimeter clusters, pT > 20 GeVPre-Higgs m`+`−j < 250 GeV

Select highest pT jet as a-candidate

≥ 2 tracks ≥ 2 tracks ghost associated to the calo jetHiggs SR 120 GeV < m`+`−j < 135 GeV

20 30 40 50 60 70 80 90 100 [GeV]

T, jet p

1

2

3

4

5

6

7

8

9610×

Eve

nts

/ 2.5

GeV

DataBackground

Za (0.5 GeV)→HZa (1.5 GeV)→HZa (2.5 GeV)→H

ATLAS-1=13 TeV, 139 fbs

100×(H)SM

σ(H)=σZa)=100%→B(H

20 30 40 50 60 70 80 90 100 [GeV]

T, jet p

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

100 110 120 130 140 150 160 170 [GeV]lljet m

0.2

0.4

0.6

0.8

1

610×

Eve

nts

/ GeV

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

100 110 120 130 140 150 160 170

[GeV]lljet m

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

S/B < 0.01

Hadronic Resonance Tagger 1428

Subtle differences in substructure of a-induced and QCD-induced jets

Substructure techniques commonplace for high-mass resonances,using wide jets and calorimeter information

Can similar techniques be applied using thin jets?

Hadronic Resonance Tagger - Tracking Detector 1528

Pixel resolution∼ 12µm in R − φand ∼ 66 (∼ 77)µm in z (R) in

the barrel (disks)

Strip resolution∼ 16µm in R − φand ∼ 580µm in z(R) in the barrel

(disks)

arXiv:1011.6665


Hadronic Resonance Tagger - Substructure Variables 1628

Input variables:

1 ∆Rlead track

2 pT, lead track/pT, tracks3 angularity(2)†

4 U1(0.7)‡

5 M2(0.3)‡

6 τ §2

0 0.05 0.1 0.15 0.2 0.25 0.3

leading track R∆

0.2

0.4

0.6

0.8

1

1.2

1.4

610×

Eve

nts

/ 0.0

05

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.05 0.1 0.15 0.2 0.25 0.3

leading track R∆

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

†arXiv:0807.0234 ‡arXiv:1609.07483 §arXiv:1011.2268





Input variables:

1 ∆Rlead track

2 pT, lead track/pT, tracks

3 angularity(2)†

4 U1(0.7)‡

5 M2(0.3)‡

6 τ §2

0 0.2 0.4 0.6 0.8 1 1.2

T, tracks/p

T, leading track p

0.5

1

1.5

2

2.5

610×

Eve

nts

/ 0.0

2

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.2 0.4 0.6 0.8 1 1.2

T, tracks/p

T, leading track p

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat






Input variables:

1 ∆Rlead track


4 U1(0.7)‡

5 M2(0.3)‡

6 τ §2

0 20 40 60 80 100 120 140 160(0.2)

tracks angularity

1

2

3

4

5

6

7

8

610×

Eve

nts

/ 2

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 20 40 60 80 100 120 140 160(0.2)

tracks angularity

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

†arXiv:0807.0234

‡arXiv:1609.07483 §arXiv:1011.2268





Input variables:

1 ∆Rlead track


4 U1(0.7)‡

5 M2(0.3)‡

6 τ §2

0 0.05 0.1 0.15 0.2 0.25(0.7)

1, tracks U

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

610×

Eve

nts

/ 0.0

05

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.05 0.1 0.15 0.2 0.25(0.7)

1, tracks U

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

†arXiv:0807.0234 ‡arXiv:1609.07483

§arXiv:1011.2268





Input variables:

1 ∆Rlead track


4 U1(0.7)‡

5 M2(0.3)‡

6 τ §2

0 0.05 0.1 0.15 0.2 0.25 0.3(0.3)2, tracks M

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8610×

Eve

nts

/ 0.0

05

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.05 0.1 0.15 0.2 0.25 0.3

(0.3)2, tracks M

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

†arXiv:0807.0234 ‡arXiv:1609.07483

§arXiv:1011.2268





Input variables:

1 ∆Rlead track


4 U1(0.7)‡

5 M2(0.3)‡

6 τ §20 0.1 0.2 0.3 0.4 0.5 0.6

2, tracksτ

0.2

0.4

0.6

0.8

1

1.2

1.4

610×

Eve

nts

/ 0.0

1

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.1 0.2 0.3 0.4 0.5 0.6

2, tracksτ

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat






0 0.05 0.1 0.15 0.2 0.25 0.3

leading track R∆

0.2

0.4

0.6

0.8

1

1.2

1.4

610×

Eve

nts

/ 0.0

05

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.05 0.1 0.15 0.2 0.25 0.3

leading track R∆

0.80.9

11.11.2

Dat

a / B

kgd

Bkgd MC Stat

0 0.2 0.4 0.6 0.8 1 1.2

T, tracks/p

T, leading track p

0.5

1

1.5

2

2.5

610×

Eve

nts

/ 0.0

2

DataBackground



100×(H)SM

σ(H)=σZa)=100%→B(H

0 0.2 0.4 0.6 0.8 1 1.2

T, tracks/p

T, leading track p

0.80.9

11.11.2

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S/B increase ∼ 5×

Hadronic Resonance Tagger - Multi-Layer-Perceptron 1728

A Multi-Layer-Perceptron (MLP) is used to combine the substructurevariables into a single, optimal summary-statistic

An MLP is machine-learning algorithm: a function, with many freeparameters, which are fixed during “training”

Hadronic Resonance Tagger - Regression 1828

Not a standard classificationproblem, due to the spectrum ofsignals

Solved by training a regressionMLP to predict ma

ma hypothesis informs classifierwhich part of the mass space toconsider

∼ 13% improvement in theexpected S/

√B

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Hadronic Resonance Tagger - Classification 1928

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Cut chosen to optimise S/√B,

assuming all a masses equallylikely: MLP > 0.052

Bkgd eff = 0.761% (MLP)

a mass / GeV 0.5 0.75 1 1.5 2 2.5 3 3.5 4

MLP Eff (%) 45.9 42.1 38.2 31.5 25.1 15.4 8.06 5.70 1.88

MLP S/√B Change 5.3 4.8 4.4 3.6 2.9 1.8 0.92 0.65 0.22

MLP S/B Change 60 55 50 41 33 20 11 7.5 2.5

Background Estimate 2028

MC is reweighted to data in: pT, Ntracks & U1(0.7)

Four regions are defined in the m`+`−j −MLP plane:

A: 120 < m`+`−j < 135 GeV and 0.052 < MLPB: 155 < m`+`−j < 175 GeV and 0.052 < MLPC: 120 < m`+`−j < 135 GeV and 0.011 < MLP < 0.052D: 155 < m`+`−j < 175 GeV and 0.011 < MLP < 0.052

Background estimate:

MC-based correction factor accounts for 13% correlation betweenm`+`−j and MLP

Background estimate of 82400, with 3.5% stat uncertainty

Background Estimate 2028

MC is reweighted to data in: pT, Ntracks & U1(0.7)

Four regions are defined in the m`+`−j −MLP plane:

A: 120 < m`+`−j < 135 GeV and 0.052 < MLPB: 155 < m`+`−j < 175 GeV and 0.052 < MLPC: 120 < m`+`−j < 135 GeV and 0.011 < MLP < 0.052D: 155 < m`+`−j < 175 GeV and 0.011 < MLP < 0.052

Background estimate:

AABCD Est.SR =

BdataCdata

Ddata︸︷︷︸Data-driven ABCD Estimate

× AMCBMCCMCDMC︸︷︷︸

MC-based ABCD Correction Factor

MC-based correction factor accounts for 13% correlation betweenm`+`−j and MLP

Background estimate of 82400, with 3.5% stat uncertainty

Validation of Background Estimate 2128

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MLP>0.052 0.034<MLP<0.052 0.026<MLP<0.034

Statistical Interpretation 2228

Single-bin cut-and-count analysis strategy adopted

Expected background:

Efficiency: (8.45± 0.22)× 10−5

Yield: 82400± 2900

Expected Signal Efficiencies and Yields (AssumingBR(h125 → Za) = 100%, and Pythia8 a BRs with tanβ = 1)

a mass / GeV 0.5 0.75 1 1.5 2 2.5 3 3.5 4

Efficiency (%) 3.3 2.8 2.9 2.5 2.0 1.3 0.69 0.51 0.14Yield (×1000) 26 22 22 20 16 10 5.4 4.0 1.1

Results 2328

MLP > 0.052

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Background: 82400± 3700 Observed events: 82908

Model-Independent Limits 2428

Fits to observed yield used to set 95% CLs upper limits

σ(h125)BR(h125 → Zηc) <110 pb

σ(h125)BR(h125 → ZJ/ψ) <100 pb

h125 → Za limits calculated for BR of a to gluons/quarks of 100%

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Outlook and Conclusion

h125 → Za Uncertainty Breakdown 2528

Impact of uncertainties on σ(pp → h125)BR(h125 → Za)/pb forthree signal hypotheses

a mass 0.5 GeV 1.5 GeV 2.5 GeV

Total Uncertainty 8.3 10.7 20.3Total Statistical Uncertainty 0.6 0.8 1.6Total Systematic Uncertainty 8.2 10.7 20.2

Signal Systematic Uncertainties

Jet Energy Scale 1.3 1.5 1.5Parton Shower 1.4 1.4 1.4

Luminosity, Pileup, Trigger, Leptons, & JVT 0.2 0.3 0.5MC Statistics 0.2 0.2 0.6

Renormalization Scale 0.1 < 0.1 0.2Acceptance 0.1 < 0.1 0.2

Background Systematic Uncertainties

MC Statistics 6.4 8.4 15.8Parton Shower and ME 3.9 5.1 9.6Renormalization Scale 3.4 4.4 8.3

What Could be Achieved? 2628

Not ATLAS work

Relevant uncertainties combined in quadrature, and limits onσ(pp → h125)BR(h125 → Za)/σSM(pp → h125) scaled down linearly,

assuming BR(a → gg) = 100%

MC Stat Modelling 0.5 GeV 1.5 GeV 2.5 GeV

3 3 31% 39% 72%7 3 20% 26% 46%7 7 7.5% 8.3% 9.7%

How to Generate Enough MC? 2728

Generate more MC?

Fully data-driven background model?

Using a Generative Adversarial Network (GAN), data can besimulated from a baseline sample (arXiv:1406.2661)

The GAN consists of two parts:

The generator, which generates data based on random numbersThe discriminator, which attempts to discriminate the generated datafrom the baseline sample

Each ‘event’ takes ∼ms, as opposed to ∼mins


Summary 2828

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Bkgd MC Stat0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

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)=100%ss→B(a

First search performed for h125 → Za→ `+`−j

Made possible by first use of track-based substructure in dual-stageMLP for light hadronic resonance identification

Limits set, starting at BR of 31%

This fills in two gaps in the previous search programme: smallBR(h125 → aa), and suppression of a decays to down-type fermions

Backup Slides

Hadronic Resonance Tagger - Track Selection 2928

Ghost-Association†

Tracks are associated to the calorimeter jet using ghost-association

The anti-kT (R = 0.4) clustering algorithm is rerun on thecalorimeter clusters, including the tracks

The tracks are treated as having very low pT so they do not influencethe calorimeter jet

Track Selection‡

Track quality requirements: ≥ 7 silicon hits, ≤ 1 shared pixel cluster,≤ 2 shared strip clusters on same layer, ≤ 1 pixel hole & ≤ 2 siliconholes

Vertexing requirements: |d0| < 2 mm & |∆z0 sin θ| < 3 mm

Jets are required to have ≥ 2 tracks surviving these requirements

†arXiv:0707.1378 †arXiv:1704.07983



Hadronic Resonance Tagger - ROC Curve 3028

5−10 4−10 3−10 2−10 1−10 1Background Efficiency

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esZa (0.5 GeV)→HZa (0.75 GeV)→HZa (1 GeV)→HZa (1.5 GeV)→HZa (2 GeV)→HZa (2.5 GeV)→HZa (3 GeV)→HZa (3.5 GeV)→HZa (4 GeV)→H

Background

SimulationATLAS-1=13 TeV, 139 fbs

higgs boson decays to light scalars at atlas · 2020. 10. 26. · atlas 2hdm+s h 125!aa summary...

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