Annual Report 2012 coepp.org.au
CoEPP – ARC Centre of Excellence for Particle Physics at the Terascale
Standard Model measurements
Various searches for new physics are being performed by CoEPP researchers. The last major discovery in particle physics before the Higgs was the observation of neutrino oscillations in the late 1990s, indicating that neutrinos must have a mass. We still do not know the mechanism by which this mass is acquired, nor whether the neutrino is what is known as a “Dirac” particle or a “Majorana” particle. This has important implications since, in the former case, one requires a finely tuned theory to explain the observed neutrino properties. In the latter case, approaches to neutrino mass generation without fine tuning exist, but they often require the existence of new particles. Kenji Hamano (Melbourne) leads LHC searches for particles arising in two different approaches to neutrino mass generation, in events with two leptons of the same sign, and events with four leptons.
An inclusive dilepton analysis (AIDA) has been performed with clear leadership from CoEPP research in a team spread across two nodes and a partner institute. Antonio Limosani (Melbourne), Andrea Bangert (Sydney) partner investigator Mark Kruse (Duke University), with contribution from Aldo Saavedra (Sydney). This analysis, the first of its type at ATLAS, makes precision simultaneous measurements of the main processes contributing to the opposite sign electron and muon final state using proton on proton collision data taken at an energy of 7 TeV. The processes include the top quark pair, W boson pair and Z to tau lepton pair production cross-sections, which are measured with precision surpassing, or competitive with, the dedicated measurements. By mapping the inclusive phase space of jet multiplicity and missing transverse energy in regions beyond where standard model processes are expected to contribute, the approach also provides a model independent search for new physics. Future iterations of AIDA will explicitly exploit this novel feature.
RESEARCH PROGRAM
Exotic new physics searches
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