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 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 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 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

scholarly journals NLO QCD+NLO EW corrections to diboson production matched to parton shower

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Mauro Chiesa ◽  
Carlo Oleari ◽  
Emanuele Re
Keyword(s):  
Parton Shower ◽  
Vector Boson ◽  
Final States ◽  
Spin Correlations ◽  
Diboson Production ◽  
Boson Pair Production ◽  
Shell Effects ◽  
Fixed Order ◽  
First Time ◽  
General Interface

AbstractWe present the matching of NLO QCD and NLO EW corrections to parton showers for vector-boson pair production at the LHC. We consider leptonic final states, including resonant and non-resonant diagrams, spin correlations and off-shell effects. Our results are obtained interfacing the Recola2-Collier one-loop provider with the framework. We discuss our implementation, we validate it at fixed order, and we show our final results matched to parton shower. A by-product of our work is also a general interface between Recola2-Collier and . This is the first time that EW and QCD corrections to diboson production are consistently matched to parton showers.

scholarly journals Spin Correlations in Top Quark Pair Production Near Threshold at the e + e - Linear Collider

2003 ◽  
Vol 40 (6) ◽  
pp. 687-692 ◽  
Author(s):  
Zhang Qing-Jun ◽  
Li Chong-Sheng ◽  
Liu Jian-Jun ◽  
Jin Li-Gang
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Linear Collider ◽  
Spin Correlations ◽  
Near Threshold

scholarly journals Two-loop leading colour QCD helicity amplitudes for top quark pair production in the gluon fusion channel

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Simon Badger ◽  
Ekta Chaubey ◽  
Heribertus Bayu Hartanto ◽  
Robin Marzucca
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Analytic Form ◽  
Gluon Fusion ◽  
Field Sampling ◽  
Massive Fermion ◽  
Iterated Integrals ◽  
Helicity Amplitudes ◽  
Complete Set ◽  
First Time

Abstract We present a complete set of analytic helicity amplitudes for top quark pair production via gluon fusion at two-loops in QCD. For the first time, we include corrections due to massive fermion loops which give rise to integrals over elliptic curves. We present the results of the missing master integrals needed to compute the amplitude and obtain an analytic form for the finite remainders in terms of iterated integrals using rationalised kinematics and finite field sampling. We also study the numerical evaluation of the iterated integrals.

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