We have calculated electron and positron states in the Nd2_/ZexCuOq compound, for the perfect bulk lattice as well as when vacancy defects are included. We study the sensitivity of the results to different approximations in the positron potential. We also compute the annihilation rate and the electron-positron momentum density using the local density approximation and the newly developed gradie...

We present the contributions from all types of one-loop corrections to the scattering amplitude for the pair production of polarized charginos or neutralinos from polarized electron-positron annihilation. The contributions are classified in terms of “prototypes” distinguished by the number of particles inside the loops and their spins. The results are quoted in terms of the Veltman-Passarino fu...

The intense 0.511 MeV gamma-ray line emission from the Galactic Center observed by INTEGRAL requires a large annihilation rate of nonrelativistic positrons. If these positrons are injected at even mildly relativistic energies, higher-energy gamma rays will also be produced. We calculate the gamma-ray spectrum due to inflight annihilation and compare it with the observed diffuse Galactic gamma-r...

The evolution and annealing of pores in, and the crystallization of, vapor-deposited films of amorphous solid water have been studied by using variable-energy positron annihilation spectroscopy for temperatures in the range 50-150 K. Both positron and positronium annihilation provide insight to the nature of the grown-in pores and their evolution with temperature. Crystallization of the films w...

Many-body theory is developed to calculate the γ spectra for positron annihilation in noble-gas atoms. Inclusion of electron-positron correlation effects and core annihilation gives spectra in excellent agreement with experiment [K. Iwata et al., Phys. Rev. Lett. 79, 39 (1997)]. The calculated correlation enhancement factors γ_{nl} for individual electron orbitals nl are found to scale with the...

We investigate, if the cosmic ray positron fraction, as reported by the HEAT and AMS collaborations, is compatible with the annihilation of neutralinos in the supergravity inspired Constrained Minimal Supersymmetric Model (CMSSM), thus complementing previous investigations, which did not consider constraints from unification, electroweak symmetry breaking and the present Higgs limits at LEP. We...

We have developed a miniature (1.2 cm2) beta-ray camera prototype to assist a surgeon in locating and removing the margins of a resected tumor. When imaging positron emitting radiopharmaceuticals, annihilation gamma ray interactions in the detector can mimic those of the betas. The extent of the background contamination depends on the detector, geometry and tumor specificity of the radiopharmac...

Division of Medical Physics, University of Leeds, UK Positron range is one important physical limitation to spatial resolution in PET imaging. We present a method to take account of positron range blurring in iterative reconstruction by including specific positron range kernels approximating the annihilation distribution in the forward projection operation [1]. The correction method is implemen...

using positron annihilation spectroscopy M. Liu, R. S. Vallery, D. W. Gidley, M. E. Launey, and J. J. Kruzic Department of Physics, Randall Laboratory, University of Michigan, Ann Arbor, Michigan 48109, USA Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA Materials Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon...