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Ultrasoft Contribution to the Positronium Hyperfine Splitting Open Access


Other title
hyperfine splitting
Type of item
Degree grantor
University of Alberta
Author or creator
Marcu, Simona Rahela
Supervisor and department
Penin, Alexander (Physics)
Examining committee member and department
Troitsky, Vladimir (Mathematics)
Prus-Czarnecki, Andrzej (Physics)
Kravchinsky, Vadim (Physics)
Department of Physics

Date accepted
Graduation date
Master of Science
Degree level
Positronium consists of an electron and positron in a bound state, a purely leptonic system and therefore an excellent test of QED (quantum electrodynamics). The ground state is characterized by two different spin configurations: spin-singlet and spin-triplet states. The difference between the corresponding energy levels is called the hyperfine splitting. Currently the discrepancy between theory and experiment is 3.9 standard deviations for this quantity. We are computing the ultrasoft contribution to the positronium hyperfine splitting. It represents the time-delayed exchange of a photon with energy of the order of the binding energy between the electron and positron. The full theoretical expression of the ultrasoft contribution was found using perturbation theory, and expansion of the positronium wavefunction at the origin about the Coulomb approximation. The expression was then evaluated using Mathematica and asymptotic approximations have been made when an exact numerical value could not be computed. The final result increases the discrepancy to 4.3 standard deviations. New experimental results are needed in order to solve the discrepancy.
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