Division of Medical Physics, University of Leeds, UK Positron range is an important spatial resolution limiting factor in PET. When imaging inside a magnetic field the positron range is non-uniformly affected. A decrease of the positron range is expected in the directions perpendicular to the direction of the magnetic field, whereas no variation is expected in the direction of the magnetic fiel...

Observations of annihilation radiation in the Galaxy are briefly reviewed. We summarize astrophysical mechanisms leading to positron production and recent estimates for production rates from nova and su-pernova nucleosynthesis in the Galaxy. The physical processes involved in the production of annihilation radiation in the interstellar medium are described. These include positron thermalization...

Annihilation or decay of dark matter (DM) could contribute to the electron and positron cosmic-ray flux, allowing for constraints on DM parameters from its measurement. CALET is directly measuring energy spectrum electron+positron cosmic rays up into TeV region most important studying heavy DM, while AMS-02 provides a positron-only below range. Limits annihilation well mass range have been deri...

By solving the Fokker-Planck equation directly we examine the effects of annihilation, particle escape and injection on the form of a steady-state positron distribution in thermal hydrogen plasmas with kT < mec. The positron fraction considered is small enough, so it does not affect the electron distribution which remains Maxwellian. We show that the escape of positrons in the form of electron-...

Introduction Range and diffusion of positron-emitting radiopharmaceuticals are important parameters for image resolution in positron emission tomography (PET). In this study, GEANT4 toolkit was applied to study positron diffusion in soft tissues with and without a magnetic field for six commonly used isotopes in PET imaging including 11C, 13N, 15O, 18F, 68Ga, and 82Rb. Materials and Methods GEA...

Positron annihilation rates in many polyatomic molecular gases are anomalously high. Qualitatively, this can be explained by positron capture in vibrational Feshbach resonances, which can occur for molecules with positive positron affinities [Gribakin, Phys. Rev. A 61 (2000) 022720]. To verify this idea quantitatively, we examine the densities of vibrational excitation spectra of alkanes. To un...