Browsing by Author "Keaveney James"

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    Anomaly detection with data quality early warning systems in ATLAS
    (2023) Msutwana, Senzo; Yacoob, Sahal; Keaveney James
    In this dissertation, the implementation of a Data-Quality Early Warning System (DQEWS) is explored. We use unsupervised Machine Learning (ML) methods to evaluate Data-Quality (DQ) in the ATLAS detector. We do so by observing and quantifying the evolution of Luminosity-Block (LB) data from Inner Detector (ID) tracking information, with a single LB towards the beginning of a run used as the reference. In this way, we obtain a trajectory that describes how the recorded LB data drift over the course of a run. Within the scope of this project thus far, the following will be shown. The version of the DQEWS algorithm defined as of the presentation of the results shown in this dissertation is shown to sufficiently flag good LBs as 'good', and bad LBs as 'bad' under the condition that the flagging criteria are evaluated on LB datasets that lie within a similar range of instantaneous luminosity as the LB datasets used to construct the criteria
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    Measurement of the top quark mass from top quarks produced in proton-proton collisions at √s = 13 TeV that decay to dimuons via a J/ψ
    (2023) Barends, Kevin; Yacoob, Sahal; Keaveney James
    The top quark mass is measured using tt → lepton + J/ψ(→ µ +µ −) events, using proton-proton collision data collected by the ATLAS detector at a centre-of-mass energy of √ s = 13 TeV, during 2015-2018. The data corresponds to a total integrated luminosity of 139.0 fb−1 . This lepton + J/ψ channel is statistically limited due to the low branching ratio of the b → J/ψ → µ +µ −. The top quark mass is measured from template fits over the m(lepton,J/ψ) distribution. The top quark mass is measured to be 172.03 ± 0.76 (stat) ± 2.14 (syst) GeV.