Measurement of fiducial and differential W+W production ...€¦ · Mateusz Dyndal (CERN) 29 Nov...

Mateusz Dyndal (CERN)

29 Nov 2019

Measurement of fiducial and differential W+W− production

cross-sections at √s=13 TeV with ATLAS

based on [ATLAS Collaboration, Eur. Phys. J. C 79 (2019) 884]

https://doi.org/10.1140/epjc/s10052-019-7371-6

M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS

▪ Good process to test the gauge structure of SM ▪ Look for signs of new physics (anomalous couplings) ▪ With more data at the LHC:

precision test of NNLO pQCD(NLO EW corrections important at the TeV scale)

Diboson production at the LHC

2

– ZZ⇤!4`

– ZZ!``⌫⌫

– ZZ!4`

ZZ

– WZ!`⌫``

WZ

– WW!eµ, [njet = 1]– WW!eµ, [njet � 0]

– WW!eµ, [njet = 0]

WW

– WV!`⌫JWV!`⌫jj

– Z�!⌫⌫�

– [njet = 0]

Z�!``�– [njet = 0]

W�!`⌫��

0.6 0.8 1.0 1.2 1.4 1.6

ratio with respect to theory

Status: July 2019

ATLAS Preliminary

Run 1,2ps = 7,8,13 TeV

NNLO QCD

NLO QCD

LHC ppps = 7 TeV

Data

statstat � syst

LHC ppps = 8 TeV

Data

statstat � syst

LHC ppps = 13 TeV

Data

statstat � syst

Diboson Cross Section Measurements


▪ Examples of recent inclusive diboson (non-WW) measurements ▪ Zy → 3% precision ▪ ZZ → 3.5% ▪ WZ→ 4.5%

Diboson production at the LHC

3

250 300 350 400 450 500 550

Integrated fiducial cross-section [fb]

(stat) (total)

ATLAS -1 = 13 TeV, 139 fbs γll)→Z(

Data 2015-2018 15.6(syst+lumi) fb± 2.1(stat) ±533.7

jj)γMATRIX NLO (incl EW Z +PDF) fb

theoryC 9.8(stat+±(scale) -18.9

+16.8444.3

jj)γMATRIX NNLO (incl EW Z +PDF) fb


+16.4518.7

jj)γ NLO EW (incl EW Z ×MATRIX NNLO +PDF) fb


+16.4510.1

jj)γMATRIX NNLO + NLO EW (incl EW Z +PDF) fb


+16.4515.3

CMS-PAS-SMP-19-001

arXiv:1911.04813

[TeV]s2 4 6 8 10 12 14

[pb]

WZ

tot.

σ

0

10

20

30

40

50

WZ → MATRIX NNLO, pp

WZ → MCFM NLO, pp

WZ→p MCFM NLO, p

ll νl→WZ-1=13 TeV, 36.1 fbsATLAS -1=8 TeV, 20.3 fbsATLAS

-1=7 TeV, 4.6 fbsATLAS -1=13 TeV, 35.9 fbsCMS

-1=8 TeV, 19.6 fbsCMS -1=7 TeV, 4.9 fbsCMS

-1=1.96 TeV, 8.6 fbsD0 -1=1.96 TeV, 7.1 fbsCDF

ATLAS

[TeV]s2 4 6 8 10 12 14R

atio

to N

LO

0.81

1.21.4

Eur. Phys. J. C 79 (2019) 535


WW production at the LHC

4

▪ Challenging experimentally ▪ Large background (top, W+jets, etc.) ▪ Fully leptonic channel → clean but neutrinos…

▪ Contribution from several sub-processes ▪ qq/qg-initiated, including TGC vertex ▪ gg-initiated (~5% of total)

▪ Recent theory developments: ▪ qq→WW known to NNLO [O(𝛼S2)]

▪ gg→WW known to NLO [O(𝛼S3)]

▪ interference known to LO [O(𝛼S2)]

Gehrmann et al., Phys. Rev. Lett. 113, 212001 (2014)

courtesy of V. Lang

Caola et al., Phys.Lett. B754 (2016) 275-280 …

Grazzini et al., JHEP 08 (2016) 140



5

▪ Irreducible background in H→W*W process and many BSM/SUSY searches

Phys.Lett. B789 (2019) 508

arXiv:1908.08215



6

▪ 8 TeV measurements revealed some data/theory tensions→ try to revisit at 13 TeV!

JHEP 1609 (2016) 029

σ1 dσ(W

W +

0 jet

s)/d∆

ϕ ℓℓ

1−10

1 Data Madgraph MC@NLO Powheg

CMS (8 TeV)-119.4 fb

Theo

ry /

Data

0.5

1

1.5

NNLOσMadgraph+Pythia normalized to

Theo

ry /

Data

0.5

1

1.5

NNLOσMC@NLO+Herwig normalized to

∆ϕℓℓ(rad)0 0.5 1 1.5 2 2.5 3

Theo

ry /

Data

0.5

1

1.5

NNLOσPowheg+Pythia normalized to

Eur. Phys. J. C 76 (2016) 401


▪ WW → eνµν decay channel is studied ▪ Same-flavour channels impacted by

large DY background

▪ Dataset: 13 TeV pp data, 36 fb-1 (2015+2016) → note full run-2 ATLAS dataset is 139 fb-1

▪ Triggers: inclusive single-lepton (OR between e and µ) ▪ pT >24 GeV (2015), >26 GeV (2016) thresholds for electrons ▪ pT >20 GeV (2015), >26 GeV (2016) thresholds for muons

▪ Measurement goals: ▪ Integrated fiducial cross-section

(also as a function of jet veto pT threshold) ▪ Differential cross-sections in 6 variables

characterising eµ dilepton system

The measurement

7


▪ Opposite-sign eµ, pT(e/µ) > 27 GeV, |ηe|<2.47, |ηµ|<2.5

▪ meµ > 55 GeV (orthogonal to H→W*W)

▪ ETmiss, track > 20 GeV ▪ pTeµ > 30 GeV

▪ No additional lepton with pT>10 GeV (to suppress WZ bkg)

▪ No jets with pT>35 GeV, |η|<4.5 (optimised for smallest total uncertainty)

▪ No b-jets (pT>20 GeV,|η|<2.5)

Event selection

8

}

}

to suppress Z→ττ

to suppress top-quark production


▪ Jet veto survival probability method (JVSP) ▪ Use data to correct predictions for top production in MC simulation ▪ Gives good systematics cancellation, esp. top modelling systematics

Top-quark background

9

allow extra jets/b-jets,HT>200 GeV

MC estimate,corrected with data


▪ Background with non-prompt (fake) lepton(s) ▪ large MC modelling uncertainties → use data-driven “matrix method”

▪ Define Loose lepton sample (looser isolation and ID requirements) ▪ Signal leptons (denoted as Tight) are subset of this sample ▪ Real (and fake) lepton efficiencies measured in data (dedicated CRs)

▪ After matrix inversion (can be done event-by-event) we can use it as:

W+jets background

10

Contribution from dijets/MJ negligible


▪ W+jets estimate validated using same-sign lepton pairs ▪ Purity not ideal (due to WZ) ▪ Good agreement with data is observed

W+jets background

11

30 40 50 60 70 80 90 100 110 120

psub−lead ℓ

T[GeV]

50

100

150

200

250

Eve

nts

/ 8

Ge

V

ATLAS-1 = 13 TeV, 36.1 fbs

Same-sign VR

DataSignal (WW)W+jetsWZZZ

TopDrell-Yan

+ tribosonγVPred. stat.

syst.⊕Pred. stat.

30 40 50 60 70 80 90 100 110 120psub− lead ℓ

T[GeV]

0.5

1

1.5

Data

/ P

red.


▪ 64% WW signal purity ▪ Nominal signal = Powheg+Pythia8 qq normalized to NNLO

+ Sherpa gg→WW normalized to NLO

▪ Largest background: top-quark production → 26%

Signal region composition

12


▪ 64% WW signal purity ▪ Nominal signal = Powheg+Pythia8 qq normalized to NNLO

+ Sherpa gg→WW normalized to NLO

▪ Largest background: top-quark production → 26%

Signal region composition

13


40 60 80 100 120 140 160 180 200 [GeV]µe

Tp

200400600800

100012001400160018002000

Even

ts /

5 G

eV ATLAS-1 = 13 TeV, 36.1 fbs

DataSignal (WW)TopW+jets

Drell-YanDi- and tribosonPred. stat.

syst.⊕Pred. stat.

40 60 80 100 120 140 160 180 200 [GeV]µe

Tp

0.60.8

11.21.4

Dat

a / P

red. 0 0.5 1 1.5 2 2.5 3

µeφΔ

200

400

600

800

1000

1200

1400

Even

ts /

0.1




syst.⊕Pred. stat.

0 0.5 1 1.5 2 2.5 3µeφΔ

0.60.8

11.21.4

Dat

a / P

red.

▪ Other control plots

Signal region

14

[GeV]miss, trackTE

20 40 60 80 100 120 140 160 180 200

Even

ts /

5 G

eV

200

400

600

800

1000

1200

1400

1600

1800Preliminary ATLAS

-1 = 13 TeV, 36.1 fbs



syst.⊕Pred. stat.

[GeV]miss, trackTE

20 40 60 80 100 120 140 160 180 200

Dat

a / P

red.

0.60.8

11.21.4 100 200 300 400 500 600 700

[GeV]µem

500

1000

1500

2000

2500

3000

Even

ts /

20 G

eV ATLAS-1 = 13 TeV, 36.1 fbs



syst.⊕Pred. stat.

100 200 300 400 500 600 700 [GeV]µem

0.60.8

11.21.4

Dat

a / P

red.


▪ Integrated fiducial cross-section:

▪ C-factor contains detector inefficiencies, and contributions from outside of the fiducial phase space (e.g. W→τν decays)

▪ Differential cross-sections:

Unfolding

15

C = 0.613 ± 0.019

Consider migrations → Split into: • Reconstruction efficiency (εj)• Fiducial correction (fi)• Unfolding matrix Mij


▪ Dominant sources: ▪ Jet calibration ▪ Background modelling

▪ Normalized differential xs: partial uncertainty cancellation

Systematic uncertaintes

16

plead ℓ

T[GeV]

210

Unc

erta

inty

[%]

0

5

10

15

20

25

30 Total Data statisticsmiss,trackT

, Eµe, Jetsb-tagging PileupW+jets +WtttOther bkgs UnfoldingPDF+scale Luminosity


plead ℓ

T[GeV]

210

Unc

erta

inty

[%]

0

5

10

15

20

25

30Total Data statistics

miss,trackT

, Eµe, Jetsb-tagging PileupW+jets +WtttOther bkgs UnfoldingPDF+scale


absolute pTl cross section

normalized pTl cross section

→ Most precise LHC WW measurement so far!


▪ Integrated fiducial cross-section ▪ Comparison to NNLO pQCD

(+NLO gg + NLO EW) calculations

Results

17

For comparison: 8 TeV measurement [JHEP 1609 (2016) 029]

For comparison: previous 13 TeV measurement [Phys. Lett. B 773 (2017) 354]


▪ Cross section as function of jet-veto pT threshold → indirect measurement of jet kinematics in the absence of jets

▪ Good stability of fixed-order NNLO in the measurement range ▪ Some data/theory trend visible

Results

18

Re et al., JHEP 1812 (2018) 121


▪ Measuring 6 differential distributions: pTlead l, meµ, pTeµ, |yeµ|, Δφeµ, |cosθ*| ▪ Comparison with:

▪ MATRIX (FO NNLO) +NLO gg +NLO EW ▪ Powheg+Pythia8/Herwig++ (NLOPS) scaled to NNLO +gg Sherpa (LOPS) scaled to NLO ▪ Sherpa 2.2 (NLOPS up to 1 extra jet, LOPS up to 2 jets) +gg Sherpa

Results

19

For comparison: 8 TeV measurement


▪ Measuring 6 differential distributions: pTlead l, meµ, pTeµ, |yeµ|, Δφeµ, |cosθ*|

Results

20




Results

21




Results

22


▪ Effect of NLO EW corrections ▪ EW corrections include QED FSR, EW loops and photon-induced

WW production

Results

23


▪ Anomalous gauge boson couplings

▪ Idea: Extend SM with dim-6 Effective Field Theory (EFT) framework:

▪ Gives rise to aTGC

▪ aGC interactions would manifest themselves as enhancement in cross-sections at high pT

Measurement interpretation

24


▪ Fit unfolded pTlead l data with EFT model

▪ SM-interference & pure-EFT terms included in templates → scale linearly or quadratically with Wilson coefficients ci

▪ Obtain limits in 3 CP-even and 2 CP-odd operators ▪ Overally more restrictive

than those derived at 8 TeV


25


▪ Comparison of EFT model limits with other measurements


26


▪ Differential WW production measured at 13 TeV by ATLAS [Eur. Phys. J. C 79 (2019) 884]

▪ Most precise WW measurement at the LHC so far ▪ Total uncertainty of 7.1% ▪ …despite much larger top-quark background wrt 8 TeV

▪ Good agreement of NNLO predictions with data, though at lower uncertainty boundary

▪ Some tensions observed → consistent with 8 TeV measurements → HO calculations needed?

▪ New limits on contributions from relevant EFT operators

▪ All measurement points (including correlations) are available at https://www.hepdata.net/record/ins1734263

Summary

27

https://doi.org/10.1140/epjc/s10052-019-7371-6

https://www.hepdata.net/record/ins1734263

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Measurement of fiducial and differential W+W production ...€¦ · Mateusz Dyndal (CERN) 29 Nov...

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