Standard Model measurements and QCD fits using ATLAS data at the LHC

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Context:Precision Standard Model (SM) measurements will be performed with the ATLAS experiment, using Run 2 and Run 3 data from the Large Hadron Collider (LHC) at CERN. The focus will be on measurements sensitive to the parton distribution functions (PDFs) of the proton, in particular those involving jets. Such measurements are also important to improve QCD modelling. The student will be actively involved in the ATLAS PDF forum, and will be a key player in new PDF determinations using LHC data, including the student's own measurements. A first ATLAS SM effective field theory (EFT) analysis, which simultaneously extracts PDFs and EFT parameters, is also expected. In addition, the student will spend some proportion of their time extending the state-of-the-art tools required for PDF determinations, in the context of the APPLfast project, which provides the technology to include new LHC cross section data in PDF determinations, and is used by all global PDF fitters world-wide. A small portion of time will also be spent working in the inclusive working group for the EPIC experiment at the EIC, studying the detector requirements for inclusive measurements.Aims and objectives: Contribute to the operation of the ATLAS detector via shifts, and authorship qualification tasks within the JetEtmiss and/or PMG group, aiming to improve pileup mitigation techniques and/or modelling. Perform analysis using the Run 2 and 3 ATLAS datasets, and investigate the impact of those measurements, and others, on constraining proton PDFs. Contribute to state-of-the-art tools, used world-wide for proton PDF determination. Publish results.Novelty of research and methodology:Measurements will be using the most precise available datasets. We expect new analysis techniques to be developed, leading also to improved systematics. New Monte Carlo simulations, and state-of-the-art calculations will be used (including in the extraction of proton PDFs). Definition of new observables, never before measured, aimed at optimising sensitivity to QCD modelling, thus providing invaluable information for improved MC simulations and more precise determinations of backgrounds to new physics searches. Development of state-of-the-art software tools for proton PDF determination which will be used world-wide. We also expect the first ATLAS standard model effective field theory analysis simultaneously extracting PDFs and EFT parameters.