Measurement of the Top Quark Polarization in the Top Quark Pair Production using the Dilepton Final State Events at the Tevatron

2018 ◽  
Author(s):  
YoungJang Lee
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Final State

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 Analysis of Top Quark Pair Production Signal from Neutral 2HDM Higgs Bosons at LHC

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Majid Hashemi ◽  
Mahbobeh Jafarpour
Keyword(s):  
Higgs Boson ◽  
Pair Production ◽  
Top Quark ◽  
Top Quarks ◽  
Higgs Doublet ◽  
Higgs Bosons ◽  
Type I ◽  
Final State ◽  
Doublet Model ◽  
Two Higgs Doublet Model

In this paper, the top quark pair production events are analyzed as a source of neutral Higgs bosons of the two Higgs doublet model type I at LHC. The production mechanism is pp→H/A→tt¯ assuming a fully hadronic final state through t→Wb→jjb. In order to distinguish the signal from the main background which is the standard model tt¯, we benefit from the fact that the top quarks in signal events acquire large Lorentz boost due to the heavy neutral Higgs boson. This feature leads to three collinear jets (a fat jet) which is a discriminating tool for identification of the top quarks from the Higgs boson resonances. Events with two identified top jets are selected and the invariant mass of the top pair is calculated for both signal and background. It is shown that the low tan β region has still some parts which can be covered by this analysis and has not yet been excluded by flavor physics data.

scholarly journals Framing energetic top-quark pair production at the LHC

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Fabrizio Caola ◽  
Frédéric A. Dreyer ◽  
Ross W. McDonald ◽  
Gavin P. Salam
Keyword(s):  
Pair Production ◽  
Momentum Transfer ◽  
Invariant Mass ◽  
Top Quark ◽  
Leading Order ◽  
Final State ◽  
Lhc Physics

Abstract Top-quark pair production is central to many facets of LHC physics. At leading order, the top and anti-top are produced in a back-to-back topology, however this topology accounts only for a minority of the events with TeV-scale momentum transfer that contain a $$ t\overline{t} $$ t t ¯ pair. The remaining events instead involve the splitting of an initial or final-state gluon to $$ t\overline{t} $$ t t ¯ . We provide simple quantitative arguments that explain why this is the case, and examine the interplay between different topologies and a range of variables that characterise the event hardness. We then develop a method to classify the topologies of individual events and use it to illustrate our findings in the context of simulated events, using both top partons and suitably defined fiducial tops. For events with large $$ t\overline{t} $$ t t ¯ invariant mass, we comment on additional features that have important experimental and theoretical implications.

scholarly journals Search for pair production of the scalar top quark in the electron+muon final state

2011 ◽  
Vol 696 (4) ◽  
pp. 321-327 ◽  
Author(s):  
V.M. Abazov ◽  
B. Abbott ◽  
M. Abolins ◽  
B.S. Acharya ◽  
M. Adams ◽  
...  
Keyword(s):  
Pair Production ◽  
Top Quark ◽  
Final State ◽  
Scalar Top
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