Highlights of top quark measurements with
the ATLAS experiment
Fabio Cardillo, on behalf of the ATLAS collaboration

20th Lomonosov Conference, 22.08.21

➡︎➡︎➡︎➡︎Introduction

Measurements of processes involving top quarks are of major importance to check predictionsof the SM and provide sensitivity to new physics beyond the SM (BSM).
In the last years, the ATLAS experiment at the LHC performed precise measurements of the
top quark properties and measured also “rare” SM processes associated with top quarks.
Will present some of the most recent and relevant results released by the ATLAS collaborationin 2021 ⇒ full list can be found here.
(I)

Measurements of the inclusive and differential production crosssections of a tt pair in association with a Z boson at √s = 13 TeV with
the ATLAS detector

arXiv:2103.12603(II) Measurement of the tttt production cross section in pp collisions at√s = 13 TeV with the ATLAS detector

arXiv:2106.11683(III) Measurements of differential cross-sections in tt events with a high pT
top quark and limits on BSM contributions to tt production with the
ATLAS detector

ATLAS-CONF-2021-31(IV) Measurement of the polarisation of single top quarks/antiquarks
produced in the t-channel collected with the ATLAS detector at√s = 13 TeV and bounds on the tWb dipole operator

ATLAS-CONF-2021-027

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

2

(I)Inclusive & differential
ttZ cross sections

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

3ttZ: Introduction
Production of top quark pairs in association with a Z boson (ttZ):
Rare process in the SM ⇒ around 1000 times smaller than tt only.
Inclusive cross-section measurement was performed by ATLAS in 2019, but without using
the full Run II dataset:‣ σttZ = 0.95 ± 0.08 (stat.) ± 0.10 (syst.) pb

Phys. Rev. D 99 (2019) 072009

Full Run II dataset (139 fb-1) provides sufficient statistics to measure this process also
differentially.
Provides access to top-Z coupling ⇒ interesting in thecontext of effective field theory (EFT) interpretations.
Important background for SM searches/measurements.
Theory predictions exist at NLO+NNLL precision⇒ see JHEP 08 (2019) 039, EPJC 80 (2020) 428.
Leptonic and hadronic decay modes of the Z boson andtt system ⇒ different lepton multiplicities in final
states.
‣ Analysis regions based on multi-lepton signatures(3l, 4l) ⇒ highest sensitivities.
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F. Cardillo-

ATLAS top-physics highlights

_
q

q

Z

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Data / SM0

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ChannelTetralepton
Trilepton
Combination (3` + 4`)
Tetralepton

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Combination (3` + 4`)

Data
ZZ+jets
tt+W/H
Uncertainty

ATLAS
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104
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-1

s = 13 TeV, 139 fb

3l + 4l SR combination
Post-fitttZ
tWZ
Fake leptons

WZ+jetstZq
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The cross section is measured to be

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Data / SM

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(b)

−2.5

−2

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0

p [GeV]
Figure6: Post-fit
distributions
the (a) andpT and(b)
rapidityof the (CR)Z bosonfor
in the combin
Simultaneous maximum-likelihood fit
in 3l/4l
signalregionsof (SR)controlregionsregions.
includes all sources of statistical and systematic(b)unce
WZ/ZZ+jets to obtain signal-strengthtetralepton
parameter:µttZThe= shaded
σData(a)/σband
SM.
fit. The lower panel shows the ratio of data to the total SM prediction. The uppermost bin
Post-fitThedistributionsof themarker(a) pT and(b)lower
rapidityof ofthe(a)
Z points
boson toin the position
combintheFigurex-axis6:ranges.
blue triangularin thepanel
Fitperformed
separately
in
3l,
4l
and
combined
3l+
4l
channels⇒consistent
results.
‣
tetralepton
regions.
The shadedband includes all sources of statistical and systematic uncer
slightly
beyondthe y-axis
range shown.
fit. The lower panel shows the ratio of data to the total SM prediction. The uppermost bins
for specific fiducial phase-space, assuming on-shell‣ Inclusive ttZ cross section is computed
the x-axis ranges. The blue triangular marker in the lower panel of (a) points to the position
decay of Z boson: 70 GeV < mll < Table
110
GeV.
slightly
beyond therange shown.
6: Measuredµt t̄y-axis
obtained from the fits in the different lepton channels.
Z parameters
statistical and systematic sources. The uncertainty of the theoretical prediction of the t t¯Z cr
and latest CMS measurement in same fiducial‣ Compatible with previous ATLASisresult
not considered for the µt t̄ Z values.
Table. 6: Measured µt t̄ Z parameters obtained from the fits in the different lepton channels.
phase-space ⇒ see JHEP 03 (2020) 056
statistical and systematic sources. The uncertainty of the theoretical prediction of the t t¯Z croµt t̄ Z
is not considered for the µtChannelt̄ Z values.
Z
T

106

1.2
1
50
0.8
−2.5

Data / SM

Data / S

ttZ: Inclusive measurement

1.21001
0.8 50

1.4
1.2
1
0.8
0.6

3l-Z

-1b4

3l-Z

-2b3

4l-S

4l-S

4l-D
F-1b

arXiv:2103.12603+0.12

1.17 ± 0.07 (stat.) 0.11 (syst.)µ t̄ Z+0.11 (syst.)
1.21 ± 0.15t(stat.)
0.10
+0.12
1.17 ± 0.07 (stat.)(syst.)
1.19 ± 0.06 (stat.) ±0.11
0.10 (syst.)
1.21 ± 0.15 (stat.) +0.11
0.10 (syst.)
1.19 ± 0.06 (stat.) ± 0.10 (syst.)(ppto!bet t¯Z) = 0.99 ± 0.05 (stat.) ± 0.08 (syst.) pb.
The cross section is measured

4l-D
F-2b

3l-W
Z

4l-Z
Z

+0.09
The result agrees withRthe SM(ppprediction
pb (stat.)at NLOand EW! t t¯Z )of= 0.84
0.99 ±
0.05± QCD
0.08 (syst.)
pb.accu
0.10
recent calculations including NNLL corrections or the complete set (QCD and EW)
Observed/predicted event yields in 3l/4l
regions
The result
agrees with the SM prediction of 0.84+0.09
15].
0.10 pb at NLO QCD and EW accu
recent calculations including NNLL corrections or the complete set (QCD and EW) o
The
contributions from the relevant uncertainties of the measured cross section are
15].
For this table, the uncertainties are grouped into several type-related categories andcontributions
fromtherelevant
the measured
cross
section5are
22.08.2021
F. Cardillo- ATLAS
top-physics
highlights
theThetotal
uncertainty.
As
noneof theuncertainties
uncertaintiesofshow
significant
asymmetries
j-PC

BT

j-PC

BT

F-1b

F-2b

-CR

-C

Table 8: Summary of the v
trilepton or tetralepton sig
separately, whereas for the
tetralepton regions are com

ttZ: Di erential measurements

Variable3✓ + 4✓

Differential cross-section measurements performed in nine observables probing
the kinematics of the ttZ system.

3✓

Absolute and normalised measurements (reduced systematics) ⇒ unfold toparticle/parton-level using Iterative Bayesian Unfolding (see here).
Evaluating compatibility between data and theoretical predictions by computing
χ2/ndf and p-values for differential distributions.
‣ All p-values > 0.05 ⇒ largest tensions in pT of Z boson and Δφ between
Z boson and tt system.
s = 13 TeV, 139 fb
3l + 4l combination

Data
MG5 aMc@NLO + Pythia8
MG5 aMc@NLO + Herwig7
Sherpa NLO inclusive
Sherpa NLO multi-leg
NLO + NNLL JHEP 08 (2019) 039

−1

6

dσ
[fb]
dNjets

ATLAS

√

dσ
[fb]
d|∆φ(t t̄, Z )|/π

dσ[fb·GeV−1]
dpTZ

8

ATLAS
10000 √
s = 13 TeV, 139 fb−1
4l SR combination

4

5000

Data
MG5 aMc@NLO + Pythia8
MG5 aMc@NLO + Herwig7
Sherpa NLO inclusive
Sherpa NLO multi-leg
NLO JHEP 08 (2019) 039

0
2.0

Stat. ⊕ Syst.

1.0
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Parton-level pTZ [GeV]

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pT(Z): parton
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Stat.

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Parton-level |∆φ(t t̄, Z )|/π|Δφ(Z,tt)|: parton
F. Cardillo

-

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1.0
0.5

Trans

|H / |

Absol

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? ✓,non-/TTrans| q(/, Clep )|

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| q(✓C+ , ✓C̄ )|Azim? TC C̄

Trans| q(C C¯, /)|

Azim

Data
MG5 aMc@NLO + Pythia8
MG5 aMc@NLO + Herwig7
Sherpa NLO inclusive
Sherpa NLO multi-leg

probes of the C C¯/ vertex
could modify the coupli

The absolute azimuthal stetralepton events provid
top quarks. The transve
hard-scattering process a

0.50

Theory
Data

Stat.

1.5

ff

s = 13 TeV, 139 fb
4l SR combination

0.25

TheoryData

Theory
Data

1.00

0.75

2

0
2.0

ATLAS

√

? T/

| H(/, Clep )|arXiv:2103.12603

Defin

In order to construct theof the leptonic top quar
quantities the reconstruct2
3≥5from 4theParticle-levelassociated
, bo
Njets
I-component of the neut
Njet: particle
in 4l
many cases the solution
the discriminant of the qwhich yields a single solu

ATLAS top-physics highlights

Stat.

Stat. ⊕ Syst.

6

(II)
Measurement of tttt
cross section

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

7tttt: Introduction
Production of four top quarks (tttt):
Very small expected cross section: σtttt = 12 ± 2.4 fb (NLO EW+QCD) JHEP 02 (2018) 031
Process sensitive to magnitude and CP propertiesof top-Higgs Yukawa coupling
Also sensitive to BSM scenarios and EFT
operators (e.g. modifying the four-fermion
couplings).
Similarly to ttZ, tttt events can give rise to various
final states covering different lepton
multiplicities.
Earlier published 2l (SS), 3l results: EPJC 80(2020) 1085 ⇒ recently combined with the resultsin the 1l, 2l (OS) channels.
Multi-lepton channels have smaller backgroundcontaminations but lower branching ratio.
‣ BR[2l (SS), 3l] = 13%, BR[1l, 2l (OS)] = 57%.
ATLAS-PHYS-PUB-2020-12
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F. Cardillo-

ATLAS top-physics highlights

8tttt: Analysis strategy
EPJC 80 (2020) 10852l(SS)/3l analysis:
Select 2l (SS) or 3l events and train boosted decision tree (BDT)
to separate tttt from background.
Use CRs for ttW and reducible background sources from fake/nonprompt leptons (e.g. heavy-flavour decays, γ-conversions).
Apply binned maximum-likelihood fit to BDT score to determineµtttt and inclusive cross section.

1l/2l(OS) analysis:

arXiv:2103.12603

Use different regions with 1l or 2l(OS) selections, further separated by
Njets and Nb-jets.
‣ Twelve regions in 1l, nine regionsin 2l (OS) channel.
All SRs have Nb-jets ≥ 3, Njets ≥ 7.
Use binned fit to different variables
to extract µtttt.
‣ BDT score in SRs & HT in CRs.
BDT scores in the 2l(SS)/3l, 1l and 2l(OS) channels
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F. Cardillo-

ATLAS top-physics highlights

9

+0.8
tttt: Results andcombinationof channels` = 2.0± 0.4 (stat.) +0.7
0.5 (syst.) = 2.0 0.6 .

fit C C¯C C¯ signal strengths for the 1L/2LOS and 2LSS/3L final states fitted separately, and for the arXiv:2103.12603
on of theResults
two final
states,(OS)are andsummarisedin analyses
Figure 12.
The fitted ` values are consistentof 1l/2l
2l (SS)/3l
deliverhe two final
states, which
are dominatedby different
and different uncertainties.
compatibleµtttt values⇒ combination
forbackgrounds
the final crossined SM section
C C¯C C¯ production
cross section is measured to bemeasurement:
fC C̄C C̄ = 24 ± 4 (stat.) +54 (syst.) fb = 24 +76 fb.

ured crosssectionis consistent
within2.0twostandard
deviations
with the SM prediction of
Most
relevantsystematics
in theanalysisare different.0 ± 2.4 fb
at NLOofin systematics
QCD including
NLO electroweak corrections [12]. The observed⇒computed
limited impact
correlations.

Higher precision in 2l (SS)/3l ⇒ dominates combined result.
24

EPJC 80 (2020) 1085

Cross section ≈ 2 times larger than SM expectation, but
within two standard deviations consistent with the latest
CMS results ⇒ see EPJC 80 (2020) 75.
22.08.2021

F. Cardillo-

1l/2l(OS) yields (top) and 2l(SS)/3l
limit (bottom)

ATLAS top-physics highlights

10(III)
Differential tt cross sections
with high top pT

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

11

tt-boosted: Analysis motivation
Boosted tt analysis:Targeting high pT (“boosted”) semi-leptonic tt events ⇒ selecting one lepton (electron/muon)
and an hadronically decaying top quark with pT > 355 GeV.
Some EFT operators and BSM scenarios expect deviations from SM for large pT or high mtt.
The tt system is fully reconstructed from the final state particles(using also large-R jets for unresolved top decays).
Inclusive/differential cross sections already measured by ATLAS
in 2019, but without full Run II data and EFT interpretations⇒ see EPJC 79 (2019) 1028.
ATLAS-CONF-2021-31

Background processes (non-tt) with at least one real lepton
estimated from MC (mostly tW). Multi-jet (0l) estimated via
matrix method (see here).
Significant impact of jet energy scale uncertainty on results.
‣ Reduced by deriving custom jet energy scale factors (JSF)
to be applied on top of the standard ATLAS calibration,
based on matching between top mass (mass of top-taggedjet) in data and MC.
‣ Best data/MC agreement for JSF = 1.0035 ± 0.00087.
22.08.2021

F. Cardillo-

mjtop in MC for different JSF values

ATLAS top-physics highlights

12

tt-boosted: Di erential measurement

Table 3:and p-values
to quanHT
HTt t̄
predictions and the respective
NNLO
top
|y
|
PWG+H7 to the P+H|y top|had
lep|y t t̄ |t t̄
mObservable
PWG+PY8
PW
extra1
Observables
Measure differential cross sections for several observables sensitivepT
22
extra2 p-value/NDFp
to kinematics of top quarks and parton shower/radiation effects.
T
top
extr a jets<0.01
pT had26/8
N
topleppT
78/8
2(extra1, top<0.01
had )Differential distributions unfolded to particle-level via Iterative
t t̄
pT
162/7
4
(extra2, top<0.01
had )Bayesian Unfolding (see ttZ analysis).
t t̄+jets
HT
36/7
<0.01
(blep, tophad
)
t t̄
HT
86/10
<0.01
3
(toplep, tophad)
Check compatibility with data (based on χ2/ndf) for several parton
tophad
|y
|
47/17
<0.01
2
(extra1, extra
2)
toplepshower algorithms and FSR/ISR variations in the MC generators.
|y|40/14 , top <0.01
1m(extra
1
had )
t t̄
extra1a jets|y |pT 30/10
vs N extr<0.01
top<0.01
extra
had
1
Use sum of bins for inclusive fiducial cross section:
mt t̄
52/10
2
p
vs
p
T
T
extra1tophadpT
115/15<0.01
3(extra
,
top
)
vs
p
1
had
T
extra2pT
σtt = 1.267 ± 0.005 (stat.) ± 0.053 (syst.) pb(extra1,46/9
tophad ) vs <0.01
N extr a jets 1
extr a jets
N
32/5
<0.01
1
ATLAS-CONF-2021-31(extra1, tophad )
17/9
0.05
(extra2, tophad )8/9
0.56(blep, tophad )95/13
3
2 <0.01(toplep, tophad )
111/5
<0.01
3
(extra1, extra2 )
24/11
0.01
1
m(extra1, tophad )
50/12
<0.01
2
extra1
extr a jetspT
vs N
355/21<0.01
20tophadextra1
pT
vs pT
115/17<0.01
5tophad(extra1, tophad ) vs pT
69/21
<0.01
4
(extra1, tophad ) vs N extr a jets
109/19<0.01
6Observable

Table 4:and p-v
predictions. PWG+
and MC@NLO+PY

top

pT(hadronic-top)ff

22.08.2021

2

pT hadtop

pT leppTt t̄
Invariant mass of tt system
No. of extra (non t-tagged)jets
t t̄+jetsHTHTt t̄
F. Cardillo- ATLAS top-physics highlights
13|y tophad |Table 4:and p-values to quantipredictions. PWG+PY8 correspondand MC@NLO+PY8 to the M Gnominal gives an estimate of the uncertainty on each variable due to missing higher-order corrections. To
be conservative, the uncertainty is included on all three variables and assumed to be uncorrelated withthe uncertainty in the other variables. The uncertainty due to the choice of the PDF set is also included.
Since all these uncertainties cover only the shape differences, an additional 6% uncertainty is included
for the uncertainty in the inclusive t t¯ cross-section. The posterior probability distribution for the Wilson
coefficients is extracted using the equation of Bayes and Laplace, as implemented in the Bayesian Analysis
Toolkit[98]. The priorprobability
distribution
the Wilson
coefficientsis taken withto be uniform.
TheMC predictions for POWHEG
Inclusive
fiducial
cross
sectionforshows
best
agreement
data forcredibility intervals for each Wilson coefficient are extracted by marginalising over the other coefficient.
MAD
GRAPH5withwith
reweighing
partonlevel.
The and
fit is also
be performed
only NNLO(QCD)+NLO(EW)
one Wilson coefficient as a free parameterand the otherat
fixedto
zero; these are referred to as individual fits.
Using differential distribution of hadronic top quark pT to derive limits on two Wilson coefficients
The expected and observed posterior distributions are shown in Figure 19. Table 5 shows the expected andmodifyingthecredibility
top-g intervals
and top-qtq(8), CtG fits. The fitted Wilson
observed
marginalised
for thecouplings:
nominal fit andC
theindividual(8)
coefficients (CtG = 0.24, Ctq= 0.03) are consistent with zero, indicating there is no evidence of ATLAS-CONF-2021-31
new(8) than latest global SMEFT
Morestringent
limitsonCtqphysics in the data. The fit prefers negative values for CtG because fewer data are observed than expected.
The result
impact of⇒theseedifferent
bins in the distribution
arXiv:2105.00006. is investigated by repeating the fit with a sub-set ofthe measured bins. Figure 20 shows the evolution of the posterior distribution as bins are added to theinterpretation. With only a single bin, the operators are degenerate and the fit can only constrain the
combination of the two. As bins are added to the fit, the ability of the fit to distinguish between the(8)operators is improved. The figure also shows that the constraining power on Ctq
by the(8)
Cistqdominatedtophadmeasurements at high pT . The observed constraints are compared to the individual limits obtained in a
recent global analysis based on multiple measurements [99] in Table 5. These limits were also obtainedusing only the EFT terms proportional to 1/⇤2 and hence can be compared to the results reported in thisnote. The limits obtained on CtG in this note are significantly weaker than these, however the limits on(8)Ctq
are more stringent than those obtained in the global fit, which, given the use of only a single dataset,
CtG
indicates that the data presented here can provide important constraining power in future
global EFT fits.

tt-boosted: Interpretations

Table 5: Expected and observed 95% intervals on the Wilson coefficients. The marginalised results show theintervals extracted from the nominal fit where both Wilson coefficients are allowed to vary. The individual intervals
are extracted from fits where only the Wilson coefficient under study is allowed to differ from zero. The results
are compared to the individual limits obtained in Ref [99]. The results quoted from Ref [99] use only the EFT
contributions proportional to 1/⇤2 in the same way as reported in this note.

Wilson coefficient
CtG
(8)
Ctq

22.08.2021

Marginalised 95% intervals
Expected
Observed[-0.44, 0.44] [-0.68, 0.21][-0.35, 0.35] [-0.30, 0.36]

Individual 95% intervals
Expected
Observed
Global fit [99][-0.41, 0.42] [-0.63, 0.20] [0.007, 0.111][-0.35, 0.36] [-0.34, 0.27] [-0.40, 0.61]

F. Cardillo-

ATLAS top-physics highlights

14

(IV)
Single-top polarisation
measurement

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

15

1 Introduction

Single-top-quark
production through the electroweak charged current at hadron colliders mostly proceeds,
Single-top polarisation: Analysis
motivationaccordingto the Standard
Model
(SM)
three modes
can becolliders
defined mostly
at leading
order
Single-top-quark
production
throughthe prediction,
electroweakvia
chargedcurrent thatat hadronproceeds,(LO)in quantum
chromodynamics(QCD):
the exchange
of a virtualboson
in theC- or inB-channel,
accordingto the Standard
Model (SM)prediction,
via threemodes,
thatcan bedefinedat theleadingorder
and theproduction of a (QCD):
top quarka , boson
At inthetheLHC,(LO)
in associatedquantum chromodynamics
theandexchangeof a (named
virtual ,C,).
boson
C- orininproton–proton
the B-channel,(?
collision
data,production
the C-channel
the dominant
and thesubjectof At
thethemeasurements
presented inand?)theassociated
of is
a top
quark andprocess
a , boson(namedC,).
LHC, in proton–proton
this?)paper.
In theC-channel
process,a light-flavour
quark @andfromof theprotons interacts
with(?
collisiondata,
the C-channel
is thedominant processtheonesubjectof colliding
the measurements
presented
inathis
1 quark,
be considereddirectly emitted
fromthe othercolliding
protonprotons(five-flavour
schemepaper. which
In the can
C-channel
process, asa light-flavourquark@ fromone ofthe colliding
interacts
withororwhichas originating
fromsingle
gluon(four-flavour
scheme4FS).
incoming
Perform first cut-based fiducial measurement
thetop-quarkpolarisation
inThe
with
fulllight-flavour
a 15FS)
quark,
canof
be consideredas splitting
directly
emittedfromtheother orcolliding
proton(five-flavour
schemequark
exchanges
a space-likeboson, (four-flavour
producing a top
quarkorC anda recoilinglight-flavour
quark
or 5FS)or as originating
fromvirtual
gluon,splitting
scheme4FS).
The incoming
light-flavour
Run II dataset.
0@ , called
the spectator
quark.virtual
Two subprocesses
contributeto theC-channel
process inlight-flavour
the productionofquark
exchanges
a space-like, boson, producing
a top
quark
C and a recoilingquark
0eithersinglequarksquark.
(C) or single
top antiquarks(C¯) at LO.toThedominant process
subprocess
is thescattering@ , called
thetopspectator
Two subprocesses
contribute
the C-channel
in theproductionofFocus on single top quarks/antiquark
production
via
exchangeofvirtualWboson
int-channelofthe single
incoming(down-)type
quark
a bottom(antiquark),
to subprocess
produce a down(up-)type
either
top upquarks(C) or single
top from
antiquarks(C¯) atquark
LO. Thedominant
is the scattering
spectatorquark
and
top quark(antiquark),
as aillustrated
inqFigure1(a) and to
Figure1(d).a The
subdominant⇒ producing a top quark/antiquark
anda recoilinglight-flavour
quarkquark(“spectator
quark”).
of theincoming
up-a(down-)type
quark frombottom(antiquark),
producedown(up-)type
subprocess
is theandscatteringof a (antiquark),
down- (up-)type
antiquarkinfrom
a bottomquark(antiquark),
produce anspectator quarka top quark
as illustrated
Figure1(a) andFigure1(d). Thetosubdominantup(down-)type
spectator
and(up-)typea top quark(antiquark),
illustrated
in Figure1(b) and
subprocess
isthevector-axial
scatteringantiquarkof a downantiquark
fromasaof
bottomquark(antiquark),
to Figureproduce1(c).
anTop quarks/antiquarks are polarisedduetovector
(V-A)
form
the
tWb
vertexThe
production cross-sectionof single
quarksabout twiceas
asillustrated
large as thatof single
antiquarks.
up- (down-)type
spectator antiquark
andtopa topquarkis(antiquark),
in Figure1(b)topandFigure 1(c).
⇒ spin aligned to down-type quarks.
The production cross-section of single top quarks is about twice as large as that of single top antiquarks.

Top-polarisation measurement in single top:

u
u

p
to

e
sp

a
ct

ar
u
rq
to

k

ar
u
q

k

b
b

d
d
W+
W+
(a)

t
t

d¯
d¯
b
b

(a)

d¯
d¯
W−
W−
(c)

W+
W+
(b)

t
t

(b)

ū
ū
b̄
b̄

ū
ū

t̄
t̄

d
d
b̄
b̄

(c)

u
u
W−
W−
(d)

t̄
t̄

(d)

Figure 1: Feynman
diagrams
for the processesfrom
contributing
to C-channel
single-top-quark
production
at LO, in the
Selecting 1l + jets events: top polarisation
vectoraccessible
angularvariablesoftheleptonfive-flavour
scheme.diagrams
In the dominant
subprocess,an up- ortodown-type
quark from one productionof the colliding
protons
Figure 1: Feynman
for the processes
contributing
C-channel single-top-quarkat LO,
in thein the top quark rest frame cos θlx´interacts
,
cos
θ
,
cos
θ
⇒
see
Phys.
Rev.
D.
89
(2014)
114009
.
with
a
1
quark
or
antiquarkfromanother
protonbyexchangingavirtual,boson
toproduce
a
(a)
top
quark
ly´
lz´
five-flavour scheme. In the dominant subprocess, an up- or down-type quark from one of the colliding protonsor(d) topwith
antiquark.
In thesubdominant
a downor up-typeaantiquarkone
the colliding
protons
interactsa 1 quarkor antiquark
fromsubprocess,another proton
by exchanging
virtual ,from
boson
to of
producea (a) topquark
interacts
with
a
1
quark
or
antiquarkfromanother
protonbyexchangingavirtual,boson
toproduce
a
(b)
top
quark
or (d) top antiquark. In the subdominant subprocess, a down- or up-type antiquark from one of the colliding protonsor(c) topwith
antiquark.
interactsa 1 quark or antiquark from another proton by exchanging a virtual , boson to produce a (b) top quark

22.08.2021

or (c) top antiquark.
F. Cardillo- ¯ ATLAS top-physics highlights

16

The QCD ? ? ! C C process produces unpolarised top quarks because of parity conservation in QCD [1–4],

Single-top polarisation: Di erential measurements
Lepton angular variables in top rest frame {cos θlx´, cos θly´ , cos θlz´} allow to determine
polarisation vector P = {Px´, Py´, Pz´} of top quark/antiquarks from a likelihood minimisation(after selecting events in SR).
Differential cross section measurement of angular variables.
‣ Unfolded to particle-level and compared to the predictions of different MC generators andparton shower algorithms (e.g. POWHEG+PY8, POWHEG+H7, MADGRAPH5+PY8).
ATLAS-CONF-2021-027

Particle-level distributions of cosθlx´ (left), cosθly´ (middle), cosθlz´ (right)
F. Cardilloff

22.08.2021-

ATLAS top-physics highlights

17

Single-top polarisation: Results and interpretations
Can set limits (∎∎) on the {Px´, Pz´} components of the top/
antitop polarisation vector.
‣ Px´ = 0.01 ± 0.18 , Pz´ = 0.91 ± 0.10 (top).
‣ Px´ = -0.02 ± 0.20 , Pz´ = −0.79 ± 0.16 (anti top).
‣ In agreement with the NLO MC prediction fromPOWHEG+PYTHIA8 (★).
Can also constrain two Wilson coefficients which
modify the tW coupling: CtW, CitW.
‣ Best-fit values are (within 68% CL) in agreement withSM expectation (CtW = CitW = 0).
‣ So far, most stringent simultaneously derived limits on
CtW and CitW.
ATLAS-CONF-2021-027<latexit sha1_base64="vRsEOVrXunfVCM+1jQlzz8ez02I=">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</latexit>

All terms
Order 1/⇤4
Order 1/⇤2

22.08.2021

CtW
68% CL 95% CL[-0.2, 0.9] [-0.7, 1.5][-0.2, 0.9] [-0.7, 1.5][-0.2, 1.0] [-0.7, 1.7]

CitW
68% CL 95% CL[-0.5, -0.1] [-0.7, 0.2][-0.5, -0.1] [-0.7, 0.2][-0.5, -0.1] [-0.8, 0.2]

F. Cardillo-

ATLAS top-physics highlights

18

Summary

Presented four of the most recent ATLAS measurements on top quark related processes (mostresults released in the last 2-3 months).
‣ Measurement of inclusive and differential ttZ cross sections in 3l and 4l final states‣ ⇒ arXiv:2103.12603.
‣ Measurement of the tttt production cross section in 1l/2l (OS) and 2l (SS)/3l channels‣ ⇒ arXiv:2106.11683.
‣ Differentials and inclusive cross section measurements of tt events with high pT top quarks‣ ⇒ ATLAS-CONF-2021-31.
‣ Measurement of top quark/antiquark polarisation in single top events‣ ⇒ ATLAS-CONF-2021-027.
Further interesting results on top physics in ATLAS can be found on the “Top Public Results”
webpage of the ATLAS collaboration (see here).

Thanks a lot for your attention!

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

19

Backup22.08.2021

F. Cardillo-

ATLAS top-physics highlights

20

ttZ analysis: Background estimation
Dominated by WZ + jets (3l) and ZZ + jets (4l) ⇒ using control
regions to constrain backgrounds (only light-jet components).

ttZ
Fakes
tZq
ZZ+jets

3l+4l SR comb.

‣ Normalisations for WZ/ZZ + light-jets free fit parameters.
WZ/ZZ + b/c-jets fixed to MC prediction (but extra unc.).

WZ+jets
tWZ
tt+X(W/H)
Other

61.2 %

0.6 %
2.0 %
2.9 %

Data-driven matrix-method for fake/non-prompt lepton background.
‣ Fake-lepton prediction validated in 3l region with Z-veto ⇒ up to
60% fake leptons.

5.0 %
6.4 %

Smaller SM backgrounds (e.g. tt+W/H, tZq, tWZ) estimated purely
from MC (all < 7%).

6.9 %
15.1 %

ATLAS

Data

WZ+jets800

s = 13 TeV, 139 fb-1

ZZ+jets

ttZ

700

3l-WZ-CR
Pre-fit

Fake leptons

Other

600

Uncertainty

ATLAS

400

s = 13 TeV, 139 fb-1

350

4l-ZZ-CR
Pre-fit

Data
Other

ZZ+jets
Uncertainty

300

500

180

ATLAS

Data

Fake Leptons

160

s = 13 TeV, 139 fb-1

WZ+jetsttZ

140

3l-1b3j-noZ
Pre-fit

tZq

tWZ

Other

Uncertainty

120
100

400

200

80

300

150

60

200

100

40

100

50

20

1.4
1.2
1
0.8
0.6

50

100

150

200

250
300
Leading lepton p [GeV]

Data / SM

250

Data / SM

Data / SM

450

Events / 100 GeV

900

EventsEvents / 30 GeV

arXiv:2103.12603

1.5
1
0.5
0

1

2

3

T

CR-3l-WZ: 1st lepton pT
22.08.2021

4

5

≥6
N jets

1.5
1
0.5
300

400

CR-4l-ZZ: Njet (pT > 25 GeV)
F. Cardillo-

ATLAS top-physics highlights

500

600

700

800

900
1000
H T [GeV]

VR-3l-Fakes: HT

21

ttZ analysis: Systematic uncertainties

Table 7: List of relative uncertainties of the measured inclusive t t¯Z cross section fromuncertainties are symmetrised for presentation and grouped into the categories described insum of the individual uncertainties is not equal to the total uncertainty due to correlations
arXiv:2103.12603

Most relevant systematics:

All detector-related uncertainties (JES/JER,
b-tag, lepton SF etc.) considered.
ttZ parton-shower (& underlying event):‣ Comparison of nominal ttZ MC(MADGRAPH5 + PYTHIA8) vs. MADGRAPH5 +HERWIG7.
tWZ modelling:‣ Comparison of different diagram removal
schemes: DR1 vs. DR2 (see here).
WZ/ZZ + jets modelling:‣ µF, µR variations & normalisation uncertainties.
‣ Extra 50% (30%) for WZ/ZZ + b(c)-jetcomponents ⇒ obtained from Z + b events (2l).

Uncertaintyt t¯Z parton showertW Z modellingb-tagging
W Z/Z Z + jets modellingt Zq modelling
LeptonLuminosity
Jets + ETmiss
Fake leptons
t t¯Z ISRt t¯Z µf and µr scales
Other backgrounds
Pile-upt t¯Z PDF
Total systematic
Data statistics
Total

t t̄ Z / t t̄ Z [%]

3.1
2.9
2.9
2.8
2.6
2.3
2.2
2.1
2.1
1.6
0.9
0.7
0.7
0.2
8.4
5.2
10

9 Differential cross-section measurements
22.08.2021

F. Cardillo-

ATLAS top-physics highlights

22

ttZ analysis: Compatibility of di erential results
Can evaluate the compatibility between data and the theoretical predictions by computing χ2/ndf
and p-values for differential distributions.
Table 9: Summary of the tests of compatibility between the unfolded differential measurements and the various
2 /ndfChecked Quoted
for different
generators,
as wellas hand-madetheoryat NLO,‣predictions.
are the ttZ
and corresponding
p-values
incorporating
all binscalculations
for the given variable
and
based
on the assumptionthat all sourcesof uncertainty
are Gaussian-distributed.
NLO+NNLL
and nNLO
precisions⇒ see JHEP
08 (2019) 039. The values associated with theadditional theory predictions (last column) are included where applicable. These additional predictions are obtained
described
in Ref.
[16], with
their precisions
dependingon theforΔφ(tt,Z).
| (t t¯, Z )| and pTt t̄ ;p-values> 0.05⇒ largest
tensionsin pT(Z),pTparticular(l non-Z),variable:
Δφ(Z, tNLOl) and‣asAllNLO+NNLL for | (Z, t lep )|, | y(Z, t lep )| and pTZ ; and nNLO for |y Z |.

pTZ
3` + 4`pTZ

X|y Z |

X
X

FigureMG5_aMC@NLO 2.3.3+P

MG5_aMC@NLO 2.3.3

8

+H

7

S

2.2.1

S

arXiv:2103.12603

2.2.1

Additional

NLO multi-leg

NLO inclusive

Theory2 /ndfp-value

2 /ndfp-value

2 /ndfp-value

2 /ndfp-value

2 /ndfp-valueX9(a)12.8/70.08

12.0/70.10

11.6/70.11

12.1/7

0.10

/

/

X

9(b)

12.8/70.08

11.7/70.11

11.2/70.13

11.3/70.13

10.4/7

0.17

X

10(a)

11.0/60.09

10.8/60.09

10.6/60.10

10.7/6

0.10

/

/

X

10(b)

11.0/60.09

10.8/60.10

10.7/60.10

10.6/60.10

10.5/6

0.11

X

11(a)

2.8/8

0.95

2.9/8

0.94

4.0/8

0.85

2.7/8

0.95

2.9/8

0.94

X

12(a)

0.8/3

0.85

0.6/3

0.90

0.3/3

0.95

0.5/3

0.92

/

/

X

pTZ

Normalised

Parton

X

pTZ

Njets

X

X

13(a)

7.6/4

0.11

8.8/4

0.07

8.3/4

0.08

8.6/4

0.07

/

/

(Z, t lep )|

X

X

13(b)

5.5/3

0.14

5.8/3

0.12

5.2/3

0.16

6.9/3

0.07

6.6/3

0.09

| y(Z, t lep )|

X

X

14(a)

0.9/3

0.82

0.7/3

0.88

0.2/3

0.98

0.5/3

0.92

0.3/3

0.96

X

12(b)

1.4/4

0.84

1.7/4

0.79

2.8/4

0.59

2.8/4

0.59

/

/

3`

pT`,non-Z
|

Njets
4`

X

Absolute

Variable

Particle‣ NLO+NNLL predictions for pT(Z) seem to show improved agreement.

|
|

X

(` +
t , ` t̄ )|

X

X

14(b)

2.1/4

0.72

2.3/4

0.69

2.7/4

0.62

2.6/4

0.63

/

/

(t t¯, Z )|

X

X

15(a)

5.2/3

0.16

4.7/3

0.19

3.5/3

0.32

3.4/3

0.33

4.9/3

0.18

pTt t̄

X

X

15(b)

3.5/4

0.47

3.6/4

0.47

3.5/4

0.48

3.5/4

0.47

4.6/4

0.33

ff

22.08.2021
F. Cardillo- section
ATLASquoted
top-physics
highlights
A difference between the measured
inclusive crossin Section
8 and the cross section

23

tttt analysis: Background estimation in 2l(SS)/3l channel
Use CRs for ttW and non-prompt electrons/muons originatingfrom heavy-flavour (HF) decays and electrons from γconversions.
Obtain normalisation factors (NFs) for these backgroundcomponents together with µtttt from simultaneous fit in all
SRs/CRs.
‣ Corrected MC is used for SM background prediction in SRs.
Parameter

NFt t̄W

NFMat. Conv.

NFLow m ⇤NFHF eNFHF µValue

1.6 ± 0.3

1.6 ± 0.5

0.9 ± 0.4

0.8 ± 0.4

1.0 ± 0.4

CR for HF electrons
22.08.2021

CR for HF muonsF. Cardillo

CR for γ-conversions-

ATLAS top-physics highlights

EPJC 80 (2020) 1085

CR for ttW24

tttt analysis: Fit regions in 1l/2l(OS)Signal and control regions are categorised by Njets and Nb-jets
in 1l and 2l (OS) channels.

arXiv:2103.12603‣ All SRs have high jet multiplicities and ≥ 3 b-jets (∎).
‣ Regions with = 3 b-jets and lower jet multiplicities (∎)
are used as CRs to fit tt+jets, separated by jet-flavour:
tt+light, tt+b, tt+c.
‣ Total tt is reweighed to data in regions with = 2 b-jets (∎)
as a function of different kinematic variables.

Njet in one of the 3b CR: pre-fit (left) and post-fit (right)
22.08.2021

F. Cardillo-

SRs/CRs in 1l and 2l(OS) channel

ATLAS top-physics highlights

25

tttt analysis: Systematic uncertainties
The nuisance parameters ranked according to their post-fit impacts on the best-fit value ofµtttt in the 1l/2l (OS) channel (left) and the 2l (SS)/3l channel (right).
Besides the tttt cross section uncertainty, different uncertainty sources are dominant for thetwo channels ⇒ no strong correlations.

EPJC 80 (2020) 1085

arXiv:2103.12603

Fit in 1l/2l(OS)22.08.2021

F. Cardillo

Fit in 2l(SS)/3l-

ATLAS top-physics highlights

26

Cross section summary plots

Summary of ATLAS and CMS measurements of
tt+X, X = W, Z, γ (left) and tttt (right) crosssections at √s = 13 TeV.
ATLAS-PHYS-PUB-2021-013

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

27

tt-boosted analysis: JSF correction
Custom correction factors to the jet energy scale (JSF) are applied to reduce the default ATLASJES uncertainties.
‣ Left: the distribution of mj top-tagged for three example values of the JSF.
‣ Middle: the mean of the same distribution as a function of JSF and a linear fit to the simulated
samples ⇒ best agreement with data for JSF = 1.0035 ± 0.00087.
‣ Right: the mj distribution observed in data compared to the expected signal and backgroundprocesses for JSF = 1.
ATLAS-CONF-2021-31

22.08.2021

F. Cardillo-

ATLAS top-physics highlights

28

tt-boosted analysis: Systematic uncertainties and EFT impact

Breakdown of systematic uncertainties for the inclusive
measurement (left) and the differential result, binned in
the top quark pT (top right).
‣ Dominant uncertainties: b-tagging, hadronisation
modelling and luminosity.
ATLAS-CONF-2021-31
SourceStatistical (data)
JSF statistical (data)

Uncertainty [%]Uncertainty [%] (no JSF)

±0.4
±0.4

±0.4
—

±0.2
±0.5
±2.0
+1.0
1.6
±0.1
+0.8
1.1
±0.7
±2.4
±0.8
±0.1
±0.4
±1.8
±0.7

±0.1
±0.8
±1.8
+1.4
2.3
±0.1

Total systematics

+4.1
4.3

+5.8
6.0

Total

+4.1
4.3

+5.8
6.0

Statistical (MC)Hard scatter
Hadronisation
Radiation (IFSR + hdamp )PDF
Top-quark massJetsb-tagging
Leptons
missET
PileupLuminosity
Backgrounds

22.08.2021

Impact of the operators Ctq(8), CtG on theparticle-level distribution of the top pT.

±0.1
±4.2
±2.4
±0.8
±0.1
±0.0
±1.8
±0.6

F. Cardillo-

ATLAS top-physics highlights

29

tt-boosted analysis: Compatibility of di erential results
Can evaluate the compatibility between data and the theoretical predictions by computing χ2/ndf
and p-values for differential distributions.
‣ Checked for different MC generators setups (variation of parton-shower algorithm and ISR/FSR).
fromPOWHEG
and MtheADagreement
GRAPH5 exist
also
extraunfolded
NNLO(QCD)+NLO(EW)‣ Predictions
Table 3: 2 andp-values
to quantify
betweenthewithabsolute
spectra, several NLO+PS
reweighing
parton-level⇒ betteragreement
data inmost cases.
predictions andatthe
respective NNLO
reweighted
spectrum.with
PWG+PY8
corresponds
to the P+Psample,PWG+H7 to the P+H

Observable

PWG+PY8
2

top
pT hadtop
pT leppTt t̄
t t̄+jetsHTHTt t̄
tophad|y|toplep
|y
|
t t̄
|y |
mt t̄
extra
pT 1
extra
pT 2
N extr a jets
(extra1, tophad )(extra2, tophad )(blep, tophad )(toplep, tophad )(extra1, extra2 )m(extra1, tophad )extra
pT 1 vs N extr a jets
top
extra
pT 1 vs pT had
top(extra1, tophad ) vs pT had(extra1, tophad ) vs N extr a jets

/NDF

p-value

26/8
78/8
162/7
36/7
86/10
47/17
40/14
30/10
52/10
115/15
46/9
32/5
17/9
8/9
95/13
111/5
24/11
50/12
355/21
115/17
69/21
109/19sample and MC@NLO+PY8 to the M

PWG+PY8(NNLO
2

)

/NDF

p-value

<0.01

5/8

<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.05
0.56
<0.01
<0.01
0.01
<0.01
<0.01
<0.01
<0.01
<0.01

28/8
46/7
7/7
37/10
27/17
17/14
8/10
24/10
38/15
19/9
12/5
8/9
5/9
34/13
36/5
16/11
20/12
205/21
53/17
43/21
64/19

MC@NLO+PY8
2/NDF

p-value

0.79

18/8

<0.01
<0.01
0.42
<0.01
0.06
0.26
0.58
<0.01
<0.01
0.02
0.03
0.53
0.84
<0.01
<0.01
0.13
0.06
<0.01
<0.01
<0.01
<0.01

144/8
171/7
17/7
110/10
37/17
29/14
23/10
81/10
413/15
25/9
76/5
150/9
8/9
145/13134/5
31/11
221/12633/21
383/17427/21545/19G

MC@NLO+PY8(NNLO
2

5_ MC@NLO + P

sample.

ATLAS-CONF-2021-31

)

/NDF

p-value

0.03

4/8

<0.01
<0.01
0.02
<0.01
<0.01
0.01
0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.57
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

10/8
22/7
23/7
16/10
23/17
12/14
6/10
7/10
194/15
74/9
78/5
80/9
25/9
16/13
82/5
69/11
48/12
316/21
152/17223/21
250/19PWG+H72

PWG+H7(NNLO/NDF

p-value

0.85

7/8

0.27
<0.01
<0.01
0.10
0.15
0.58
0.81
0.74
<0.01
<0.01
<0.01
<0.01
<0.01
0.23
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

43/8
122/7
21/7
47/10
30/17
28/14
14/10
29/10
143/15
42/9
57/5
42/9
85/9
52/13
90/5
237/11
41/12
263/21
121/17
78/21
85/19

2

)

/NDF

p-value

0.56

3/8

0.94

<0.01
<0.01
<0.01
<0.01
0.03
0.01
0.19
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

18/8
39/7
12/7
28/10
26/17
19/14
7/10
22/10
69/15
29/9
62/5
30/9
76/9
25/13
36/5
215/11
19/12
159/21
74/17
60/21
60/19

0.02
<0.01
0.10
<0.01
0.07
0.16
0.74
0.02
<0.01
<0.01
<0.01
<0.01
<0.01
0.02
<0.01
<0.01
0.08
<0.01
<0.01
<0.01
<0.01

ff

Table 4: 2 and p-values to quantify the agreement between the absolute unfolded spectra and several NLO+PS
22.08.2021
F. Cardillo-+ P ATLAS
top-physics highlights
predictions. PWG+PY8 corresponds to the P
sample, PWG+H7 to the P+Hsample30

Single-top polarisation: Systematic uncertainties

Left: extracted values for the different components of the top quark/antiquark polarisation vectors
P = {Px´, Py´, Pz´}, together with background normalisations from the CRs.
Right: statistical and systematic uncertainties (grouped by categories) in the measurement of thepolarisation-components for top quarks/antiquarks.
ATLAS-CONF-2021-027<latexit sha1_base64="hb5IiGuZrz2qr9uiJokrj/ser5k=">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</latexit><latexit sha1_base64="jKOHE9pdc7fpqXuFffbGWbdnXqo=">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</latexit>

Parameter

Extracted value(stat.)

t-channel norm.
W +jets norm.
tt̄ norm.

+1.045 ± 0.022+1.148 ± 0.027+1.005 ± 0.016( ± 0.006)( ± 0.005)( ± 0.004)+0.01 ± 0.18

( ± 0.02)

Pxt0
Pxt̄0
Pyt0
Pyt̄0
Pzt0
Pzt̄0

22.08.2021

0.02 ± 0.20
0.029 ± 0.027( ± 0.03)( ± 0.011)+0.91 ± 0.10

( ± 0.02)

0.007 ± 0.051
0.79 ± 0.16

( ± 0.017)( ± 0.03)

Uncertainty source
Modelling
Modelling (t-channel)
Modelling (tt̄)
Modelling (other)
Experimental
Jet energy scale
Jet energy resolution
Jet flavour tagging
Other experimental uncertainties
Multijet estimation
Luminosity
Simulation statistics
Total systematic uncertainty
Total statistical uncertainty

F. Cardillo

-

Pxt0

Pxt̄0

Pyt0

Pyt̄0

Pzt0

Pzt̄0

±0.037±0.016±0.013±0.051±0.021±0.031±0.010±0.004±0.003±0.015±0.016±0.006±0.061±0.003±0.026±0.061±0.016±0.043±0.045±0.166±0.004±0.015±0.008±0.001±0.020±0.174±0.017±0.048±0.185±0.002±0.029±0.021±0.001±0.024±0.199±0.025±0.005±0.021<0.001±0.002<0.001<0.001±0.008±0.025±0.011±0.007±0.040±0.001±0.007±0.001<0.001±0.015±0.048±0.017±0.033±0.070±0.007±0.014±0.008<0.001±0.017±0.096±0.022±0.025±0.130±0.009±0.026±0.013<0.001±0.031±0.153±0.034ATLAS top-physics highlights

31

Single-top polarisation: Data-compatibility and EFT impact<latexit sha1_base64="VIX+oQZ06L1gkitgYvGyC0Xmo5I=">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</latexit>

Compatibility between the SM prediction and data
for the unfolded differential distributions of cos θlx´,
cos θly´ and cos θlz´ (χ2/ndf and p-values).

Angular variablecos ✓`x0cos ✓`y0cos ✓`z02/NDF
1.53/7
4.25/72.98/3p-value
0.98
0.75
0.39

Impact of CtW and CitW on the unfolded spectra of cos θlx´ and cos θly´ ⇒ the particle-level prediction
from the SM (∎) can be compared to the result from the best-fit values of CtW and CitW (∎).
ATLAS-CONF-2021-027

Particle-level distributions of cosθlx´ (left) ad cosθly´ (right)
22.08.2021

F. Cardillo-

ATLAS top-physics highlights

32