scholarly journals Spin correlation effects in top quark pair production at the LHC

2010 ◽  
Vol 81 (7) ◽  
Author(s):  
Gregory Mahlon ◽  
Stephen J. Parke
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Spin Correlation ◽  
Correlation Effects

SPIN CORRELATION EFFECTS IN THE HADROPRODUCTION AND DECAY OF VERY HEAVY TOP QUARK PAIRS

1989 ◽  
Vol 04 (03) ◽  
pp. 617-625 ◽  
Author(s):  
V. BARGER ◽  
J. OHNEMUS ◽  
R. J. N. PHILLIPS
Keyword(s):  
Top Quark ◽  
Spin Correlation ◽  
Weak Decay ◽  
Tree Level ◽  
Matrix Elements ◽  
Correlation Effects ◽  
Quark Pairs ◽  
Quark Spin ◽  
Dilepton Events ◽  
Top Quark Pairs

Density matrix techniques in the helicity basis allow us to write down explicitly the squared matrix elements for tree-level hadroproduction and weak decay of very heavy top quark pairs, that decay before hadronization. This treatment includes the full effects of quark spin correlation. We illustrate the effects of spin correlation on physical distributions in [Formula: see text] dilepton events, [Formula: see text], [Formula: see text], [Formula: see text], for the case mt =120 GeV at [Formula: see text], the energy of the Tevatron collider. The effects of spin correlation are quantitatively small compared to calculations that ignore them, giving corrections of order 10% or less in the physical distributions studied.

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 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 Top quark pair production near threshold: single/double distributions and mass determination

2020 ◽  
Vol 2020 (6) ◽  
Author(s):  
Wan-Li Ju ◽  
Guoxing Wang ◽  
Xing Wang ◽  
Xiaofeng Xu ◽  
Yongqi Xu ◽  
...  
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Mass Determination ◽  
Near Threshold

scholarly journals Search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Production Cross ◽  
Branching Fraction ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Third Generation ◽  
Final State ◽  
Generation Scalar ◽  
Scalar Leptoquarks

Abstract A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton is presented. The search is based on a dataset of pp collisions at $$ \sqrt{s} $$ s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Events are selected if they have one light lepton (electron or muon) and at least one hadronically decaying τ -lepton, or at least two light leptons. In addition, two or more jets, at least one of which must be identified as containing b-hadrons, are required. Six final states, defined by the multiplicity and flavour of lepton candidates, are considered in the analysis. Each of them is split into multiple event categories to simultaneously search for the signal and constrain several leading backgrounds. The signal-rich event categories require at least one hadronically decaying τ-lepton candidate and exploit the presence of energetic final-state objects, which is characteristic of signal events. No significant excess above the Standard Model expectation is observed in any of the considered event categories, and 95% CL upper limits are set on the production cross section as a function of the leptoquark mass, for different assumptions about the branching fractions into tτ and bν. Scalar leptoquarks decaying exclusively into tτ are excluded up to masses of 1.43 TeV while, for a branching fraction of 50% into tτ, the lower mass limit is 1.22 TeV.

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