ATLAS delivers new direct measurement of the top-quark decay width with improved precision | 8/1/2019 | Staff
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As the heaviest known particle, the top quark plays a key role in studies of fundamental interactions. Due to its short lifetime, the top quark decays before it can turn into a hadron. Thus, its properties are preserved and transferred to its decay products, which can in turn be measured in high-energy physics experiments. Such studies provide an excellent testing ground for the Standard Model and may provide clues for new physics.

A key parameter examined by the ATLAS Collaboration at CERN is the top quark's "decay width", which is related to the particle's lifetime and decay modes. Decays resulting from new physics might alter the decay width, making its precise measurement particularly important. In the Standard Model, theoretical calculations predict a value for the decay width of 1.32 GeV for a top-quark mass of 172.5 GeV.

ATLAS - Collaboration - Measurement - Decay - Width

The ATLAS Collaboration presented a new measurement of the top-quark decay width at the Lepton Photon Symposium in Toronto, Canada. The analysis makes use of the full dataset from Run 2 the Large Hadron Collider (LHC)—with a corresponding integrated luminosity of 139 fb−1 – to provide ATLAS' best precision yet.

The new analysis takes a direct approach to the measurement of the top-quark decay width. ATLAS physicists selected collision events where top-quark pairs decay into two charged leptons (electrons or muons) of opposite electric charge. This decay channel has a higher purity of signal events and smaller systematic uncertainties compared to alternative channels. ATLAS measured the invariant...
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