Carleton The ATLAS Group

Higgs Analysis

The primary goal of the ATLAS Experiment was the search for a particle known as the Higgs Boson. This particle was postulated by our leading theory of sub-atomic physics, the Standard Model (SM), as the reason ordinary matter has mass. In July 4th, 2012, the discovery of a particle consistent with the SM Higgs Boson was announced (link:!  This discovery heralded the end of the Discovery era, and start of the Measurement era at the LHC, where the properties of this newly discovered Boson will be measured with the highest precision. Measurement of the properties of the Higgs boson is a powerful probe into our understanding of the SM and sub-atomic physics, as well as detector performance.

Studies are are being undertaken by graduate students Kate Whalen, James Lacey, Graham Cree, and David Di Valentino to measure the properties of the newly discovered Higgs Boson. These studies analyze the decays of the Higgs into four electrons or muons (via Z bosons), or two photons (via fermion loop).  These studies have focused on (i) measuring backgrounds produced by non-Higgs interactions which mimic the Higgs (KW), (ii) measuring cross sections by searching for specific production modes involving quark jets, called Vector Boson Fusion (JL+DDV) (iii) measuring the mass of the Higgs through models of how the detector responds to individual decay products (GC). An understanding of all aspects of the newly found boson is crucial to determining its role in the sub-atomic nature of matter.