Standard Model@UCL

The combination of electroweak unification and Quantum ChromoDynamics (QCD), usually referred to as the Standard Model of particle physics, is the most powerful scientific theory ever developed, being able to describe with unprecedented precision millions of experimental datapoints measured over decades of particle physics, and having successfully predicted the existence of the Higgs boson. The unprecedented centre-of-mass energy of the LHC allows the Standard Model (SM) to be extensively explored above the electroweak symmetry breaking scale for the first time, in a huge variety of final states. The UCL group makes fundamental contributions to this work at ATLAS, with an emphasis on making model-independent measurements of well-motivated final states in well-defined fiducial regions. Our current activities cover:

• Measuring the production of jets as a test of QCD, including jets production, jet vetoes, azimuthal correlations and jets including from heavy quarks.
• UCL also pioneered a new line research in jets, jet substructure, to determine whether they are produced by quarks, gluons, or hadronic decays of heavy particles like W, Z or Higgs bosons, or top quarks. We continue to improve these algorithm and lead analyses measuring production of W and Z bosons in their hadronic decays and searches for new particles decaying into bosons.
• Measurement of the tau-pair production cross section
• The interpretation of these and other measurements to set model-independent constraints on physics beyond the SM (see also our exotic physics page and Contur)

Past results have included:

• Model-independent measurement of missing energy
• Measurement of the production of vector bosons in association with jets
• Measurement of the production of vector bosons in their hadronic decay modes
• Electroweak production of Z bosons
• Measurement of the differential cross section as a function of the four-lepton invariant mass
• First measurements of charged particle multiplicities in early LHC data

For more information, contact Jon Butterworth or Mario Campanelli.