The rate of annihilation of low-energy positrons in many molecular gases is orders of magnitude larger than can be explained on the basis of simple collisions. Developments in positron beam technology have enabled the first energy-resolved measurements of this annihilation process. The results of these experiments provide direct evidence that the large observed values of annihilation rate are d...

Described here is a proposed experiment to use laser-assisted photorecombination of positrons from a trap-based beam and metal atoms in the gas phase to measure positron–atom binding energies. Signal rates are estimated, based in part upon experience studying resonant annihilation spectra using a trapbased positron beam. While positrons are important in many areas of science and technology incl...

The principle of image formation in tomography is summarised. The principle ofpositron electron annihilation is introduced. The principle of coincidence techniques is illustrated. Detector development and perspectives for positron emission tomography (PET) instrumentation for medical research is presented. The physical processes in in positron annihilation, photon scattering and tomograph desig...

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has been observing gammaray lines from the Sun and the Galaxy since its launch in February 2002. Here I summarize the status of RHESSI observations of solar lines (nuclear de-excitation, neutron capture, and positron annihilation), the lines of Al and Fe from the inner Galaxy, and the search for positron annihilation in novae.

The possibility is examined for the inclusive Λ in unpolarized electron-positron annihilation to be transversely polarized. Due to final-state interactions, there exists a novel structure function F̂ (z,Q) for the inclusive Λ hyperon (or any other baryons) production from the unpolarized time-like photon fragmentation, which makes contribution to the transverse Λ polarization in the unpolarized ...

A bstract We study capability of the ILC beam dump experiment to search for new physics, comparing performance electron and positron dumps. The dark photon, axion-like particles, light scalar bosons are considered as physics scenarios, where all important production mechanisms included: electron-positron pair-annihilation, Primakoff process, bremsstrahlung productions. find that has higher sens...

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 spectroscopy is nowadays well recognised as a powerful tool of microstructure investigations of condensed matter. An overview of the method aimed for users from other fields is given and supplemented with several examples of applications.

We present first-principles approaches based on density functional theory for calculating positron states and annihilation characteristics in condensed matter. The treatment of the electron-positron correlation effects (the enhancement of the electron density at the positron with respect to mean-field density) is shown to play a crucial role when calculating the annihilation rates. A generalize...

In a positron-sensitive probe composed of a plastic scintillator and a bismuth germanate (BGO), scattered annihilation photons in the plastic scintillator become background counts. Although these scattered annihilation photons can be rejected by higher threshold level settings for the scintillation pulse of the plastic scintillator and for that of the BGO, the system sensitivity is reduced. We ...