Precision Measurements of the Standard Model: PDFs, Pile-up, and Production of W+jets at 13 TeV with the ATLAS Detector

Context:
Precision Standard Model measurements will be performed, of vector boson (W/Z) + jet production, using the full Run 2 dataset from the Large Hadron Collider (LHC) at CERN. Such measurements are important to improve our understanding and modelling of these processes (important also in the context of new physics searches, where V+jet often constitute significant backgrounds). The student will in particular be responsible (at least in the first instance) for the W+jet measurement in the muon channel, which is currently uncovered, so there is substantial opportunity to make a leading contribution from the start. V+jets processes are also sensitive to proton structure, and the measurements performed will be used by the student (together with other data from HERA and the LHC) to determine improved proton parton distribution functions (PDFs). 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. In addition, there will be significant opportunity for the student to expand into other areas in later years, including new physics searches, or Higgs measurements.

Aims and objectives:
Contribute to the operation of the ATLAS detector via shifts, and authorship qualification tasks within the JetEtmiss group, aiming to improve pileup mitigation techniques. Perform analysis using the full Run 2 ATLAS dataset, 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 the most precise to date (using the full Run 2 dataset). 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. Possible first measurements of rare Higgs decay channels.