Measurements of multi-boson productions including
vector-boson fusion and vector-boson scattering at ATLAS

Rongkun Wang1
on behalf of the ATLAS collaboratio
Aug 19 2021 @ 20th Lomonosovn

1. Harvard University

Multi-boson Physics
Electroweak production, powerful tool to probe the Standard Model• Vector boson scattering(VBS) directly probes gauge boson selfinteractions, non-Abelian structure of the EW interactions• Rare processes provides discovery opportunities•ATL-PHYS-PUB-2021-032
Rongkun Wang

20th Lomonosov

2Outline•

VBS processes•Observation of EW ZZjj

•Fiducial cross-section measurements of ew
NZ(—>ll)γjj••Search for Z(—>vv)γjjw
eNObservation of WWW tri-boson process NewRongkun Wang

20th Lomonosov

3

Observation of EW ZZjj
Very rare process with a ducial cross section of ~1fb
• Prevent unitarity violation at TeV scale• Decay channel ZZ—> 4l, ZZ—>llνν• |ΔYjj| > 2, mjj > 300 for 4l (400 for llvv)• BDT is trained to distinguish between EWK and QCD
ZZjj, largely using jet-related variables, mjj, |ΔYjj|, pTjets…
• Fitting on the BDT score, gives μEW=1.35±0.34, withsigni cance of 5.5(4.3) σ. μQCD=0.96±0.22•

Submitted to Nature Physics arXiv:2004.10612

20th Lomonosov
fifiRongkun Wang

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Measurement of Z(—>ll)γjj
Probes the non-SM neutral
quartic gauge couplings.
• VBF topology: large rapidity
gap between the jets
|ΔYjj| > 1• Centrality of llγ relative tothe tagging jets

Events / bin

•

1000
900
800
700

SRATLAS Preliminarys = 13 TeV, 139 fb-1
Pre-fit
CRDataEW-Zγ jjQCD-Zγ jj
Z+jetsttγWZTotal unc.

600500400300200•

ζ < 0.4 as signal region,
ζ > 0.4 as control region

Rongkun Wang

DataPrediction

100
00
1.4
1.2
10.8
0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2
ζ(llγ )

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

22.2

ζ(llγ )ATLAS-CONF-2021-038

20th Lomonosov

5Measurement of Z(—>ll)γjj
Simultaneous t in SR and CR on mjj distribution••

μEW, μQCD-SR, μQCD-SR

EWK ducial XS:•4.49 ± 0.4(stat.) ± 0.42(syst.)f b<latexit sha1_base64="zpD0LcPb8ZzeATgVTg91Lgew5AU=">AAACEXicbZDLSgMxFIYzXmu9jbp0EyxC3QwzdfCyK7pxWcFeoC0lk2ba0ExmSM4IpfQV3Pgqblwo4tadO9/GTFtBW38I/PnOOSTnDxLBNbjul7W0vLK6tp7byG9ube/s2nv7NR2nirIqjUWsGgHRTHDJqsBBsEaiGIkCwerB4Dqr1++Z0jyWdzBMWDsiPclDTgkY1LGLvuNf4lYSYdfxcVEDAefk514yYKgzEAYdu+A67kR40XgzU0AzVTr2Z6sb0zRiEqggWjc9N4H2iCjgVLBxvpVqlhA6ID3WNFaSiOn2aLLRGB8b0sVhrMyRgCf098SIRFoPo8B0RgT6er6Wwf9qzRTCi/aIyyQFJun0oTAVGGKcxYO7XDEKYmgMoYqbv2LaJ4pQMCHmTQje/MqLplZyvDPn9NYvlK9mceTQITpCReShc1RGN6iCqoiiB/SEXtCr9Wg9W2/W+7R1yZrNHKA/sj6+AXosmQ8=</latexit>•Measured:

4.73 ± 0.01(stat.) ± 0.15(P DF )+0.23
0.22 (scale)f b<latexit sha1_base64="uoCcc+cMJt0bwFozmbz9Q8FekSo=">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</latexit>

Pred:

•

Observation of well over 10 σ

QCD process included:•Events / bin••Measured:•Predicted(MG5):

800
700

Data
EW-Zγ jj
QCD-Zγ jj
Z+jetsttγ
WZ
Total unc.

ATLAS Preliminarys=13 TeV, 139 fb-1

600

SR
Pre-Fit

500
400
300
200

Data / Pred.

100
01.2
1.1
10.9
0.85001000fifi

Rongkun Wang

1500

2000

2500
3000mjj [GeV]

20th Lomonosov

6Observation of Z(—>vv)γjj•

First observation of Z(νν)γjj
with 5.2(5.1) σ signi cance•|Δηjj| > 3, mjj > 250 GeV•Δφjj < 2.5 to suppressmultijet•

Using multiple control
region to constrain
background during the t•

Measured signal strength
μEW = 1.03±0.25•

Also sets limits on invisible
Higgs decay

EXOT-2021-17
fi

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Triboson - WWW

One of the rarest SM processes, sensitive to aTGC/aQGC• Off-shell WH—>WW* is also included as signal• Two channels:• WWW—>l±vl±vjj, same-sign di-leptons plus 2 jets
• More channels based on lepton avor: ee, eμ, μμ• WWW—>l±vl∓vl±v, no same- avor opposite-sign
lepton pairs•

ATLAS-CONF-2021-039

fl

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Triboson - WWW
Signal region:• mll, ETmiss to suppress Z+jets• Train separate BDT in 2l and 3lchannels• Variables include mjj, pT(jet),jet multiplicity, mll, pT(lep),
ETmiss…
• Main background: WZ,constrained by SFOS control
region during simultaneous twith signal• Other data-driven background:
non-prompt, γ conversion(Vγ),
charge- ip• Other SM backgroundestimated by MC•

20th Lomonosov
fiflRongkun Wang

9WWW 2l channel
500

400

Post- t data/MC comparison
ATLAS Preliminarys = 13 TeV, 139 fb-1
SR 2l
Post-Fit

Data
WWW(µ=1.66)
WZ
Non-prompt
γ conv.
Charge-flip
Other
Uncertainty
Pre-Fit Bkgd.

EventsEvents / 16 GeV

•120
100

ATLAS Preliminarys = 13 TeV, 139 fb-1
SR µ± µ±Post-Fit

Data
WWW(µ=1.66)
WZ
Non-prompt
Other
Uncertainty
Pre-Fit Bkgd.

8030060200

4010001.4
1.2
10.80.6020406080100120140160m jj [GeV]

fiRongkun Wang

Data / Pred.

Data / Pred.

2001.41.2
10.8
0.6
00.1 0.2

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0.3

0.4

0.5

0.6

0.7

0.8

0.9

12l BDT output

10

WWW 3l channel

60

ATLAS Preliminarys = 13 TeV, 139 fb-1
SR 3l
Post-Fit

DataWWW(µ=1.66)
WZ
Non-prompt
γ conv.
Charge-flip
Other
Uncertainty
Pre-Fit Bkgd.

Events / 1.570

Post- t data/MC comparison
403530502540203015201010501.4
1.2
10.80.6001.4
1.2
10.80.6050 100 150 200 250 300 350 400 450 500m lll [GeV]

fiRongkun Wang

Data / Pred.

Data / Pred.

Events / 100 GeV•ATLAS Preliminarys = 13 TeV, 139 fb-1
SR 3l
Post-Fit

246

Data
WWW(µ=1.66)
WZ
Non-prompt
γ conv.
Charge-flip
Other
Uncertainty
Pre-Fit Bkgd.

8101214EmisssignificanceT

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Triboson - WWW•

Signal strength<latexit sha1_base64="3i83YCW5yT78ouzr9O4aO8CUDKc=">AAACBXicbVDNS8MwHE3n15xfVY96CA5BEEYrQ70IQy8eJ7gPWMtI03QLS5qSpMIou3jxX/HiQRGv/g/e/G9Mtx5080Hg5b33I/m9IGFUacf5tkpLyyura+X1ysbm1vaOvbvXViKVmLSwYEJ2A6QIozFpaaoZ6SaSIB4w0glGN7nfeSBSURHf63FCfI4GMY0oRtpIffvQpEOK8wu8gh5PoYdDoaGCpzDo21Wn5kwBF4lbkCoo0OzbX14ocMpJrDFDSvVcJ9F+hqSmmJFJxUsVSRAeoQHpGRojTpSfTbeYwGOjhDAS0pxYw6n6eyJDXKkxD0ySIz1U814u/uf1Uh1d+hmNk1STGM8eilIGtYB5JTCkkmDNxoYgLKn5K8RDJBHWpriKKcGdX3mRtM9q7nmtflevNq6LOsrgAByBE+CCC9AAt6AJWgCDR/AMXsGb9WS9WO/WxyxasoqZffAH1ucPb/SXPg==</latexit>

prediction = µ · s + b

Total observed(expected) signi cance of 8.2(5.4) σ• Also measured production cross section• 850 ± 100 (stat.) ± 80 (syst.) fb•

Fit

Observed (expected) significances [ ]µ(W W W )

e± e±
e± µ±
µ± µ±2`
3`
Combined

2.3 (1.4)
4.6 (3.1)
5.6 (2.8)
6.9 (4.1)
4.8 (3.7)
8.2 (5.4)

1.69 ± 0.79
1.57 ± 0.40
2.13 ± 0.47
1.80 ± 0.33
1.33 ± 0.39
1.66 ± 0.28

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Summary•

VBS EWK ZZjj processes observed with 5.5σ (4.3σ expected)•Fiducial cross section of Z(—>ll)γjj processes measured to be
4.49±0.58 fb•

Z(—>vv)γjj is observed for the rst time 5.2σ (5.1σ expected)•WWW processed is observed for the rst time 8.2σ (5.4σexpected)fi

20th LomonosovfiRongkun Wang

13backup

Z(—>ll)γjj phase space

Rongkun Wang

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WWW BDT variables

Rongkun Wang

20th Lomonosov

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WWW yield

Rongkun Wang

20th Lomonosov

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WWW data/mc plots

Rongkun Wang

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WWW uncertainty
Uncertainty source
Data-driven background
Prompt-lepton-background modeling
missJets and ET
MC statistics
LeptonLuminosity
Signal modeling
Pile-up modeling
Total systematic uncertainty
Data statistics
W Z normalizations
Total statistical uncertainty
Rongkun Wang

20th Lomonosov

/ [%]
5.3
3.3
2.8
2.8
2.11.9
1.5
0.9
9.5
11.2
3.3
11.6
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