Thesis

Search for single top quark production via FCNC 4-Fermion operators

• Call:

  IDPASC Portugal - PHD Programme 2014

• Academic Year:

  2014 /2015

• Domain:

  Experimental Particle Physics

• Supervisor:

  Filipe Veloso

• Co-Supervisor:

  Rui Santos

• Institution:

  Universidade de Coimbra

• Host Institution:

  Laboratório de Instrumentação e Física Experimental de Partículas

• Abstract:

  The top quark is the heaviest elementary particle known, with a mass close to the electroweak symmetry breaking, and it can provide clues about the symmetry breaking and the Higgs mechanisms. It is thus an excellent object to test the Standard Model of Particle Physics (SM). There is an important effort to study the top quark properties, like its mass, production cross-sections, electric charge, spin, decay asymmetries, rare decays, etc... Deviations from SM predictions of the production and decay properties of the top quark provide model-independent tests for physics beyond the SM. According to the SM, the top quark decays nearly 100% of the time to a W boson and a b quark. Flavour changing neutral current (FCNC) decays are forbidden at tree level by the GIM mechanism and are allowed at one-loop level with a branching ratio of the order of 10^-14. Several SM extensions predict a higher BR for top quark FCNC decays, such as 10^-4. The search for FCNC decays can be done using effective operators such as 4-Fermion, and provide thus a way for verify the validity of the SM and test the existence or restrict SM extensions. This research program will be developed within the Portuguese ATLAS group and aims to search LHC data (collected by the ATLAS detector) for single top quark production via FCNC 4-Fermion operators or to set 95%CL limits in the absence of signal.