scholarly journals Probing the spin correlations of $$t{\bar{t}} $$ production at NLO QCD+EW

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Rikkert Frederix ◽  
Ioannis Tsinikos ◽  
Timea Vitos
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Correlation Coefficients ◽  
Spin Correlation ◽  
Spin Correlations ◽  
Scale Uncertainty ◽  
Narrow Width Approximation ◽  
Uncertainty Band ◽  
Fixed Order ◽  
Narrow Width

AbstractIn this work we investigate the NLO QCD+EW corrections to the top quark pair production and their effects on the spin correlation coefficients and asymmetries at fixed-order top quark pair production and LO decay in the dilepton channel, within the narrow-width approximation. The spin correlations are implicitly measured through the lepton kinematics. Moreover we study the EW effects to the leptonic differential distributions. We find that the EW corrections to the $$t {\bar{t}}$$ t t ¯ production are within the NLO QCD theoretical uncertainties for the spin correlation coefficients and the leptonic asymmetries. On the other hand, for the differential distributions we find that the EW corrections exceed the NLO QCD scale uncertainty band in the high rapidity regimes and are of the order of the NLO QCD scale uncertainty in the case of invariant mass and transverse momentum distributions.

scholarly journals NNLO QCD corrections to leptonic observables in top-quark pair production and decay

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Michał Czakon ◽  
Alexander Mitov ◽  
Rene Poncelet
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Absolute Threshold ◽  
Spin Correlations ◽  
Narrow Width Approximation ◽  
Level Data ◽  
Complete Study ◽  
Fixed Order ◽  
Narrow Width ◽  
First Time

Abstract We calculate a comprehensive set of spin correlations and differential distributions in top-quark pair production and decay to dilepton final states. Our calculation is performed in the Narrow Width Approximation. This is the first time such a complete study is performed at next-to-next-to leading order in QCD. Both inclusive and fiducial distributions are presented and analyzed. Good agreement between NNLO QCD predictions and data is found. We demonstrate that it is possible to perform high-precision comparisons of fixed-order calculations with fiducial-level data. Subtleties of the top quark definition are raised and clarified. Some of those are found to have a very significant impact on top-quark pair production at absolute threshold.

scholarly journals Measurements of top-quark pair spin correlations in the $$e\mu $$ channel at $$\sqrt{s} = 13$$ TeV using pp collisions in the ATLAS detector

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
M. Aaboud ◽  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
...  
Keyword(s):  
Cross Sections ◽  
Differential Cross ◽  
Top Quark ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Absolute Difference ◽  
Opening Angle ◽  
Differential Cross Sections ◽  
Spin Correlations ◽  
Fixed Order

Abstract A measurement of observables sensitive to spin correlations in $$t\bar{t}$$tt¯ production is presented, using 36.1 $$\hbox {fb}^{-1}$$fb-1 of pp collision data at $$\sqrt{s} = 13$$s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider. Differential cross-sections are measured in events with exactly one electron and one muon with opposite-sign electric charge as a function of the azimuthal opening angle and the absolute difference in pseudorapidity between the electron and muon candidates in the laboratory frame. The azimuthal opening angle is also measured as a function of the invariant mass of the $$t\bar{t}$$tt¯ system. The measured differential cross-sections are compared to predictions by several NLO Monte Carlo generators and fixed-order calculations. The observed degree of spin correlation is somewhat higher than predicted by the generators used. The data are consistent with the prediction of one of the fixed-order calculations at NLO, but agree less well with higher-order predictions. Using these leptonic observables, a search is performed for pair production of supersymmetric top squarks decaying into Standard Model top quarks and light neutralinos. Top squark masses between 170 and 230 GeV are largely excluded at the 95% confidence level for kinematically allowed values of the neutralino mass.

scholarly journals Maximizing spin correlations in top quark pair production at the Tevatron

1997 ◽  
Vol 411 (1-2) ◽  
pp. 173-179 ◽  
Author(s):  
Gregory Mahlon ◽  
Stephen Parke
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Spin Correlations

scholarly journals Spin correlations in top-quark pair production at e+e− colliders

1996 ◽  
Vol 387 (1) ◽  
pp. 199-206 ◽  
Author(s):  
Stephen Parke ◽  
Yael Shadmi
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Spin Correlations

scholarly journals Subleading EW corrections and spin-correlation effects in $$t\bar{t}W$$ multi-lepton signatures

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Rikkert Frederix ◽  
Ioannis Tsinikos
Keyword(s):  
Phase Space ◽  
Cross Section ◽  
Top Quark ◽  
Spin Correlation ◽  
Top Quarks ◽  
Correlation Effects ◽  
Spin Correlations ◽  
Decay Products ◽  
Theoretical Predictions ◽  
The Impact

AbstractRecently a slight tension between data and predictions has been reported in $$t\bar{t}W$$ t t ¯ W production by both the CMS and ATLAS collaborations. We revisit the theoretical predictions for this process, focussing on the following two effects. We disentangle various effects that lead to asymmetries among the leptonic decay products of the (anti-)top quarks and W bosons, for which we find that the spin correlations in the top-quark pair are the dominant source. We also discuss the impact of the large, formally subleading, electroweak corrections to $$t\bar{t}W$$ t t ¯ W production at the LHC. We find that this effect changes the $$t\bar{t}W$$ t t ¯ W cross section significantly in the signature phase-space regions, and should therefore be included differentially in the theory to data comparisons.

scholarly journals Higher Order Corrections to Spin Correlations in Top Quark Pair Production at the LHC

2019 ◽  
Vol 123 (8) ◽  
Author(s):  
Arnd Behring ◽  
Michał Czakon ◽  
Alexander Mitov ◽  
Rene Poncelet ◽  
Andrew S. Papanastasiou
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Higher Order ◽  
Spin Correlations ◽  
Higher Order Corrections
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