On the trapping rate of positrons in deformed lead over the temperature range 4–100 K

The trapping of positrons in annealed and plastically deformed samples of lead has been studied over the temperature range 4–100 K. The rate of trapping by defects has been found to be independent of temperature — a finding that supports the golden rule positron trapping model.     

A vertical positron beam for low-temperature surface studies

A cryostat system incorporating a low-energy positron beam for surface measurements down to Temperatures below 2 K is currently under construction at the Royal Holloway and Bedford New College. The positron beam has recently been brought into operation and its operating characteristics have been evaluated. Positrons from a²²Na source are converted with an efficiency of =2×10^–4 and transported magnetically at 1.5 V above the work function to a target at the bottom of a cryostat. The transmission of a 7 mm diameter beam is found to be constant over a range of axial field strengths from 40 to 50 G.This paper is based upon a poster presented at the International Symposium Production of Low-Energy Positrons with Accelerators and Applications (Justus-Liebig-Universität Giessen, FRG, 25–27 September, 1986)     

Masses of S and P wave mesons and pseudoscalar decay constants using a confinement scheme

In the framework of relativistic harmonic confinement model for quarks and antiquarks, the masses of S- and P-wave mesons and pseudoscalar decay constants from light flavour to heavy flavour sectors are computed. The residual two-body Coulomb interaction and the spin-dependent interaction of the confined one gluon exchange effects (COGEP) such as spin-spin and spin-orbit interactions are perturbatively incorporated with the confinement energy to get the respective vector-pseudoscalar meson mass differences. Here we employ the same parametrization and model parameters as used in a recent study of low-lying hadron masses and leptonic decay widths. The results are being compared with the values obtained from other theoretical models and the experimental values.     

Evidence for zero-point motion of positrons in metals

The Doppler-broadened photon spectra arising from positrons annihilating in a single crystal of cadmium have been studied over the temperature range from 4.2 K to its melting point. Line shape analysis provides evidence for zero-point motion of positrons trapped in vacancies.     

On the origin of dark spaces in plasmas

Regular dark space patterns in discharges in neon/helium mixtures arising from pulsed electric fields are shown to be related to dark rings in Lichtenberg figures. They offer the prospect of a new approach in the study of the formation of striations.