scholarly journals Top quark pair property measurements using the ATLAS detector at the LHC

2016 ◽  
Author(s):  
Mohammad Kareem
Keyword(s):  
Top Quark ◽  
Atlas Detector ◽  
Pair Property

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.

scholarly journals Search for FCNC single top-quark production at s=7 TeV with the ATLAS detector

2012 ◽  
Vol 712 (4-5) ◽  
pp. 351-369 ◽  
Author(s):  
G. Aad ◽  
B. Abbott ◽  
J. Abdallah ◽  
A.A. Abdelalim ◽  
A. Abdesselam ◽  
...  
Keyword(s):  
Top Quark ◽  
Atlas Detector ◽  
Single Top ◽  
Top Quark Production ◽  
Quark Production

scholarly journals Measurements of top quark properties with the ATLAS detector

2015 ◽  
Vol 95 ◽  
pp. 04073
Author(s):  
Christopher Unverdorben
Keyword(s):  
Top Quark ◽  
Atlas Detector

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.

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