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20 May 2018

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 activities cover:

  • Measuring the production of jets (including jets from heavy quarks), and jet substructure
  • 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
  • Study of the gluon splitting into pairs of b-quarks, the main background to the dominant decay of Higgs bosons
  • The interpretation of these and other measurements to set model-independent constraints on physics beyond the SM (see also our exotic physics page)
We also made the first measurements of charged particle multiplicities in early LHC data

Key Academics

Jon Butterworth
Mario Campanelli
Gavin Hesketh
Emily Nurse

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

  • ATLAS Collaboration, Charged-particle multiplicities in pp interactions at sqrt(s) = 900 GeV measured with the ATLAS detector at the LHC Phys.Lett.B688:21-42,2010
  • M Botje, J Butterworth, A Cooper-Sarkar, A de Roeck, J Feltesse, S Forte, A Glazov, J Huston, R McNulty, T Sjostrand, R Thorne, The PDF4LHC working group interim recommendations arXiv:1101.0538 [hep-ph]
  • ATLAS Collaboration, Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC New J.Phys.13:053033,2011
  • ATLAS Collaboration, Measurement of inclusive jet and dijet production in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector Eur.Phys.J.C71:1512,2011, Phys.Rev. D86 (2012) 014022
  • J Butterworth, S Carrazza, A Cooper-Sarkar, A De Roeck, J Feltesse, S Forte, J Gao, A Glazov, J Huston, Z Kassabov, R McNulty, A Morsch, P Nadolsky, V Radescu, J Rojo, R Thorne, PDF4LHC recommendations for LHC Run II J. Phys. G: Nucl. Part. Phys. 43 023001 (2016)
  • ATLAS Collaboration, Measurement of b-hadron pair production with the ATLAS detector in proton-proton collisions at 8 TeV, JHEP 11 (2017) 62, arXiv:1705.03374
  • ATLAS Collaboration, Measurement of WW/WZ to ll qq production with the hadronically decaying boson reconstructed as one or two jets in pp collisions at 8 TeV with ATLAS, and constraints on anomalous gauge couplings, European Physical Journal C, 77 (8) (2017), doi:10.1140/epjc/s10052-017-5084-2 
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