Browsing by Subject "LHC"
- Results Per Page
- Sort Options
Item Open Access A Measurement of the Production Cross Section of a Single Top Quark in Association with a $W$-boson at $\sqrt{s} = 13$ TeV with the ATLAS Detector at the Large Hadron Collider(2020) Davis, DouglasA measurement of the Standard Model cross section for the production of a single top quark in association with a $W$-boson from proton-proton collisions is presented. Collision data at a center-of-mass energy of 13 TeV totaling 139 inverse femtobarns collected by the ATLAS detector on the Large Hadron Collider is used to study the process. Binary classifiers trained using kinematic properties of observable particles are used to separate the signal process from a large top pair production background. A binned maximum likelihood fit is performed to extract the Standard Model cross section for the signal process, along with a secondary top pair cross section measurement and uncertainties related to object reconstruction with the detector and theoretical models. The measured cross section is the most precise measurement performed using the ATLAS detector and is in good agreement with the Standard Model prediction.
Item Open Access A Search for Supersymmetry in Multi-b Jet Events with the ATLAS Detector(2019) Epland, Matthew BergA search for supersymmetry in pair-produced gluinos decaying via top squarks to the lightest neutralino is presented. Events with multiple hadronic jets, of which at least three must be identified as originating from b-quarks, and large amounts of missing transverse energy in the final state, are selected for study. The dataset utilized encompasses proton-proton collisions with a center-of-mass energy of sqrt(s) = 13 TeV and integrated luminosity of 79.9 fb-1 collected by the ATLAS experiment at the LHC from 2015 to 2017. The search employs a parameterized boosted decision tree (BDT) to separate supersymmetric signal events from standard model backgrounds. New methods for optimal BDT parameter point selection and signal region creation, as well as new soft kinematic variables, are exploited to increase the search's expected exclusion limit beyond prior analyses of the same dataset by 100-200 GeV in the gluino and neutralino mass plane. No excess is observed in data above the predicted background, extending the previous exclusion limit at the 95% confidence level by 250 GeV to approximately 1.4 TeV in neutralino mass. The analytical and machine learning techniques developed here will benefit future analysis of additional Run 2 data from 2018.