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22 Feb 2024

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 points 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 an unprecedented 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 (including jets from heavy quarks), and jet substructure
  • Study of the gluon splitting into pairs of b-quarks, the main background to the dominant decay of Higgs bosons
  • Model-independent measurement of missing energy
  • 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)
Past results have included:
  • 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

Key Academics

Jon Butterworth
Mario Campanelli

Leadership positions

Jon Butterworth Standard Model Group Convener 2010-2012, PDF4LHC contact
Mario Campanelli Jets subgroup Convener 2015-2016, PDF convener 2017-2018
Emily Nurse Soft-QCD Physics subgroup convenor 2010-2011

Key References

The mass of jets passing the selection for WW final stated. The mass peak around the W mass of 80 GeV (in red) allowed the measurement of the WW cross-section in the topology with a lepton plus a a single jet, resulting from the hadronic decay of boosted W and Z bosons.

See also