Top Quark Mass and Properties Measurements with the ATLAS Detector

The top quark is the heaviest elementary particle and unique among the known quarks since it decays before forming hadronic bound states. This makes measurements of the top quark itself particularly interesting as one can access directly the properties of a bare quark. The latest measurements of these properties with the ATLAS detector are reported using data from 8 TeV and 13 TeV proton-proton collisions at the Large Hadron Collider at CERN. The latest measurements of the top quark mass using template methods, as well as others aiming to measure the mass in a well-defined scheme, are presented. In addition, measurements for the top quark decay width, top quark spin observables and [Formula: see text]-boson helicity in events with top quark pairs ([Formula: see text]) are presented and compared to the Standard Model predictions. The cross-section measurements of top quark pair production in association with a photon, [Formula: see text]- or [Formula: see text]-boson are also reported and compared to the most accurate theoretical calculations. These measurements probe the top quark electroweak couplings. Limits on the rate of flavour-changing neutral current processes in the production or decay of the top quark are also shown.

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Top-quark properties and mass measurements with the ATLAS detector

EPJ Web of Conferences ◽

10.1051/epjconf/201818202033 ◽

2018 ◽

Vol 182 ◽

pp. 02033

Author(s):

Tomas Dado ◽

Keyword(s):

Top Quark ◽

Bound States ◽

W Boson ◽

Theoretical Calculations ◽

Atlas Detector ◽

Spin Density Matrix ◽

Top Quark Mass ◽

Quark Pairs ◽

Quark Spin ◽

Top Quark Pairs

The top quark is unique among the known quarks in that it decays before it has an opportunity to form hadronic bound states. This makes measurements of its properties particularly interesting as one can access directly the properties of a bare quark. The latest measurements of these properties with the ATLAS detector at the LHC [1] are presented. Measurements of top-quark spin observables in top-antitop events, each sensitive to a different coefficient of the spin density matrix, are presented and compared to the Standard Model predictions. The helicity of the W boson from the top decays and the production angles of the top quark are further discussed. Limits on the rate of flavour changing neutral currents in the production or decay of the top quark are reported. The production of top-quark pairs in association with W and Z bosons is also presented. The measurement probes the coupling between the top quark and the Z boson. The cross-section measurement of photons produced in association with top-quark pairs is also discussed. These process are all compared to the best available theoretical calculations. The latest ATLAS measurements of the top-quark mass in lepton+jets, dilepton, and all-hadronic final states are also reported. In addition, measurements aiming to measure the mass in a well-defined scheme are presented.

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POSSIBLE EXISTENCE OF TOPPED HADRONS

International Journal of Modern Physics A ◽

10.1142/s0217751x95001509 ◽

1995 ◽

Vol 10 (22) ◽

pp. 3143-3153

Author(s):

TOSHIAKI ITO ◽

SHOJI SAWADA

Keyword(s):

Binding Energy ◽

Top Quark ◽

Quark Mass ◽

Bound States ◽

Vacuum Expectation ◽

Higgs Doublet ◽

Top Quark Mass ◽

Unitarity Bound ◽

Top Quark Decay ◽

Quark Decay

We study possibilities of formation of the topped hadrons, the [Formula: see text], [Formula: see text], tqq, ttq and ttt bound systems. We assume that the inverse of binding energy is the parameter of the formation time of the bound system and take the ratio Γtotal/EB as a criterion for the formation of these hadrons, where EB and Γtotal are a binding energy and a total decay width of a topped system respectively. We take into account the binding force caused by the Higgs scalar exchange as well as the one-gluon exchange. It is shown that there is no possibility of forming the single top quark hadrons before the top quark decay. In the standard model, where only one Higgs doublet contributes, among the topped hadrons only toponium [Formula: see text] and the three-top-quark baryon Ωttt with the top quark mass less than 140 GeV and 130 GeV have a possibility of forming the bound states before their decay. In the case of the two-Higgs-doublet model we show that there is a possibility of forming the topped hadrons, toponium, Ξtt and Ωttt for the larger top quark mass if the ratio of vacuum expectation values of two Higgs scalars is large near to the unitarity bound.

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