Thesis

Measurement of top quark rare decay t->sW at ATLAS

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domain:

  Experimental Particle Physics

• Supervisor:

  Filipe Veloso

• Co-Supervisor:

  Patricia Conde Muino

• 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. The Cabbibo-Kobayashi-Maskawa (CKM) quark mixing matrix is related to the rates of the Flavour Changing Charged Current (FCCC) decay modes. Some of the elements were not yet directly measured but are determined from the unitarity conditions of the matrix. The present estimated value for the Vts element is (42.0+-2.7)×10-3. A direct measurement of these elements put strict conditions on the assumptions behind the matrix properties, as the existence of only three families on the SM. This research program will be developed within the Portuguese ATLAS group. It aims to measure the decay rate of the top quark into a W boson plus a s-quark with LHC data collected by the ATLAS detector. This result will then be used to measure also the amplitude of the CKM element Vts.