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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]
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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
theoryC 12.2(stat+±(scale) -14.9
+16.4518.7
jj)γ NLO EW (incl EW Z ×MATRIX NNLO +PDF) fb
theoryC 12.2(stat+±(scale) -14.9
+16.4510.1
jj)γMATRIX NNLO + NLO EW (incl EW Z +PDF) fb
theoryC 12.2(stat+±(scale) -14.9
+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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
WW production at the LHC
5
▪ Irreducible background in H→W*W process and many BSM/SUSY searches
Phys.Lett. B789 (2019) 508
arXiv:1908.08215
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
WW production at the LHC
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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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.
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
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
ATLAS-1 = 13 TeV, 36.1 fbs
DataSignal (WW)TopW+jets
Drell-YanDi- and tribosonPred. stat.
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
DataSignal (WW)TopW+jets
Drell-YanDi- and tribosonPred. stat.
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
DataSignal (WW)TopW+jets
Drell-YanDi- and tribosonPred. stat.
syst.⊕Pred. stat.
100 200 300 400 500 600 700 [GeV]µem
0.60.8
11.21.4
Dat
a / P
red.
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
ATLAS-1 = 13 TeV, 36.1 fbs
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
ATLAS-1 = 13 TeV, 36.1 fbs
absolute pTl cross section
normalized pTl cross section
→ Most precise LHC WW measurement so far!
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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]
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ Measuring 6 differential distributions: pTlead l, meµ, pTeµ, |yeµ|, Δφeµ, |cosθ*|
Results
20
For comparison: 8 TeV measurement
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ Measuring 6 differential distributions: pTlead l, meµ, pTeµ, |yeµ|, Δφeµ, |cosθ*|
Results
21
For comparison: 8 TeV measurement
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ Measuring 6 differential distributions: pTlead l, meµ, pTeµ, |yeµ|, Δφeµ, |cosθ*|
Results
22
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ Effect of NLO EW corrections ▪ EW corrections include QED FSR, EW loops and photon-induced
WW production
Results
23
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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
Measurement interpretation
25
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ Comparison of EFT model limits with other measurements
Measurement interpretation
26
M. Dyndal29 Nov 2019 W+W− production at √s=13 TeV with ATLAS
▪ 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