summary eft top polarization

Probing the tWb structure in t- channel single top-quark

production using the ATLAS detector at the LHC

Galo Gonzalvo Rodríguez

06-02-2020

• In the t-channel at LO, as a consequence of the V-A form of the tWb vertex, single top quarks are

produced with their spin completely aligned along the direction of the down-type quarks (Phys.

Rev.D55(1997) 7249).

• Since the top-quark lifetime is shorter than the

depolarisation timescale (10^-21 s), the top-quark spin information is directly transferred to its decay

products.

2 ²

INTRODUCTION

3 ³

αl: spin analysing power associated with the final state charged lepton (~1 at LO) Pi: Top-quark degree of polarisation in a given direction i

z axis: along the direction of the spectator jet in the top quark reference frame y axis: perpendicular to the direction of the incoming light quark and the spectator jet x axis: perpendicular to the z and y axis

1 d

dcos✓_`i = 1

2 (1 + ↵`Pi cos✓`i) with i = x, y, z

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• The angular distributions of the top-quark decay products are sensitive to its polarisation (Phys.

Rev. D53 (1996) 4886):

• Using a proper coordinate system, as proposed in (Phys. Rev. D89 (2014) 114009) one can obtain the differential angular distributions associated with the three different polarisation components {PX,PY,PZ}.

• In this analysis these angular differential distributions are measured in order to compare with theoretical predictions.

• Deviations from SM predictions can give hints of physics beyond the SM (the measurement can be interpreted within an EFT framework in terms of tWb anomalous couplings or Wilson coefficients).

INTRODUCTION

INTRODUCTION

• Deviations from SM predictions of the unfolded differential measurements can give hints of physics beyond the SM (the measurement can be interpreted within an EFT framework in terms of tWb

anomalous couplings or Wilson coefficients).

• Plots comparing the unfolded differential measurements with the predictions from beyond the SM models are provided. In an EFT framework:


• 


In single-top t-channel production (for massless b-quarks) at LO QCD and at O(1/Λ²), only three operators with three coefficients are required to parametrize new physics effects: 


• In terms of anomalous couplings, the most general effective tWb interaction arising from a minimal set of dimension-six effective operators was found to be:

4 ⁴

DSID samples: 412076, 412077, 412079
 (aMC@NLO+Py8)

DSID samples: 410916-20,410996
 (Protos+Py8)

UNFOLDED DIFFERENTIAL MEASUREMENTS COMPARING WITH WILSON COEFFICIENTS SAMPLES

• INCLUSIVE

5 ⁵

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Data/Pred.

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3

ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data (expected) Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8

aMC@NLO+Py8 ictW c1p75 ctW c2 aMC@NLO+Py8 ictW c1p75 aMC@NLO+Py8 ctW c2 aMC@NLO+Py8

θY

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Data/Pred.

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3 0.35

0.4 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data (expected) Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8

aMC@NLO+Py8 ictW c1p75 ctW c2 aMC@NLO+Py8 ictW c1p75 aMC@NLO+Py8 ctW c2 aMC@NLO+Py8

Sensitive to Real part Sensitive to Imaginary part

UNFOLDED DIFFERENTIAL MEASUREMENTS COMPARING WITH WILSON COEFFICIENTS SAMPLES

• INCLUSIVE

6 ⁶

θl

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Data/Pred.

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ATLAS Internal

= 13 TeV , 139.0 fb-1

s

Data (expected) Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8

aMC@NLO+Py8 ictW c1p75 ctW c2 aMC@NLO+Py8 ictW c1p75

aMC@NLO+Py8 ctW c2 aMC@NLO+Py8

UNFOLDED DIFFERENTIAL MEASUREMENTS COMPARING WITH ANOMALOUS COUPLINGS SAMPLES

• INCLUSIVE

7 ⁷

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Data/Pred.

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3

ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data (expected) Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 = 0.32 /VL

= 0.4; gL

/VL

VR

Protos+Py8 = -0.18 )/VL

Re (gR

= 0.18 )/VL

Re (gR

= -0.07 /VL

Im gR

= 0.07 /VL

Im gR

= -0.32 /VL

= -0.4; gL

/VL

VR

θY

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Data/Pred.

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3 0.35

0.4 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data (expected) Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 = 0.32 /VL

= 0.4; gL

/VL

VR

Protos+Py8 = -0.18 )/VL

Re (gR

= 0.18 )/VL

Re (gR

= -0.07 /VL

Im gR

= 0.07 /VL

Im gR

= -0.32 /VL

= -0.4; gL

/VL

VR

Sensitive to Real part Sensitive to Imaginary part

UNFOLDED DIFFERENTIAL MEASUREMENTS COMPARING WITH WILSON COEFFICIENTS SAMPLES

• INCLUSIVE

8 ⁸

θl

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Data/Pred.

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data (expected) Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8

= 0.32 /VL

= 0.4; gL

/VL

VR

Protos+Py8 = -0.18 )/VL

Re (gR

= 0.18 )/VL

Re (gR

= -0.07 /VL

Im gR

= 0.07 /VL

Im gR

= -0.32 /VL

= -0.4; gL

/VL

VR

BACKUP

• The most general effective tWb interaction arising from a minimal set of dimension-six effective operators is (Nucl.Phys. B812 (2019)):

• Given the current limits (JHEP 04 (2017) 124), the following anomalous couplings samples have been studied in this analysis:

10 ²⁷

BEYOND THE STANDARD MODEL: ANOMALOUS COUPLINGS

11 ¹⁹

Comparisons with different MC predictions at particle level Uncertainty sources: Mainly dominated by jet energy resolution.

FINAL RESULTS: UNFOLDED ANGULAR DISTRIBUTIONS

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25

1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15 0.2 0.25 0.3

ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

θY

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15 0.2 0.25 0.3 0.35

0.4 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

Work in progress Work in progress

12 ²⁰

Comparisons with different MC predictions at particle level Uncertainty sources: Mainly dominated by jet energy resolution.

FINAL RESULTS: UNFOLDED ANGULAR DISTRIBUTIONS

θl

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.1 0.2 0.3 0.4 0.5 0.6 0.7

0.8 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7 Work in progress

13

Unfolded differential measurements for top quarks and antiquarks

22

UNFOLDED ANGULAR DISTRIBUTIONS: TOP AND ANTITOP

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25

0.3 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3

ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

Top Antitop

Work in progress Work in progress

14 ³¹

UNFOLDED ANGULAR DISTRIBUTIONS: TOP

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3

ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

θY

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3 0.35

0.4 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

Work in progress Work in progress

15 ³²

UNFOLDED ANGULAR DISTRIBUTIONS: TOP

θl

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25

1.5

θ/dσ d⋅σ1/

0.1 0.2 0.3 0.4 0.5 0.6 0.7

0.8 ATLAS Internal

= 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7 Work in progress

16 ³³

UNFOLDED ANGULAR DISTRIBUTIONS: ANTITOP

θX

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15 0.2 0.25

0.3 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

θY

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.05 0.1 0.15

0.2 0.25 0.3 0.35

0.4 ATLAS Internal = 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

Work in progress Work in progress

17 ³⁴

UNFOLDED ANGULAR DISTRIBUTIONS: ANTITOP

θl

cos

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

Pred./Data

0.5 0.75 1 1.25 1.5

θ/dσ d⋅σ1/

0.1 0.2 0.3 0.4 0.5 0.6 0.7

0.8 ATLAS Internal

= 13 TeV , 139.0 fb-1

s

Data Stat. Unc.

Stat. + Sys. Unc.

POWHEG + Py8 Protos+Py8 aMC@NLO+Py8 POWHEG+H7

Work in progress

• Particle-level objects are constructed from stable particles of the MC event record (ME+PS) with a lifetime > 0.3 · 10^-10 s within the observable pseudorapidity range.

• These objects do not take into account any detector effect or any additional pp interactions (pile- up).

• More info: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/ParticleLevelTopDefinitions

18 ³⁵

PARTICLE LEVEL OBJECTS DEFINITION