Ph.D. Project 2015-2018 Positron interaction with many-electron atoms

State of the art and motivations The positron is the antiparticle of the electron. It was the first “piece ” of antimatter to have been discovered, first theoretically by Paul Dirac in 1931, and then experimentally by Carl Anderson in 1932. Both physicists were awarded the Nobel Prize, Dirac in 1933, and Anderson in 1936. Positrons are also the simplest and most abundant form of antimatter. They are produced in β+ decays of radioactive nuclei, can be generated in accelerators, and are observed in large quantities (about 15 × 109 tonnes per second!), emerging from an unknown source near the centre of our Galaxy. The ability of positrons to annihilate with electrons and produce characteristic annihila-tion gamma rays, is behind their use in various diagnostics, from positron lifetime spectroscopy of solids to positron emission tomography (PET) in medicine. When partnered with antiprotons, positrons can form antihydrogen, currently under intense investigation at CERN. Positron interaction with atoms is an interesting and physically rich subject. Because of the repulsion from positively charged atomic nuclei, the electrostatic interaction between a positron and an atom is repulsive. However, electron correlations, i.e., a dynamic response of the atomic electrons to the presence of the positron, gives rise to positron-atom attraction. Such attractio