In condensed matter initially fast positrons annihilate after having reached equi librium with the surroundings. The interaction of positrons with matter is governed by the laws of ordinary quantum mechanics. Field theory and antiparticle properties enter only in the annihilation process leading to the emergence of energetic photons. The monitoring of annihilation radiation by nuclear spectroscopic methods provides valuable information on the electron-positron system which can directly be related to the electronic structure of the medium. Since the positron is a positive electron its behavior in matter is especially interesting to solid-state and atomic physi cists. The small mass quarantees that the positron is really a quantum mechanical particle and completely different from any other particles and atoms. Positron physics started about 25 years ago but discoveries of new features in its interac tion with matter have maintained continuous interest and increasing activity in the field. Nowadays it is becoming part of the "stock-in-trade" of experimental physics.

This book provides a comprehensive and up-to-date account of the field of low energy positrons and positronium within atomic and molecular physics. Each chapter contains a blend of theory and experiment, giving a balanced treatment of all the topics. Useful for graduate students and researchers in physics and chemistry.

With the exception of positron emission tomography (PET), the field of low energy positron science produces relatively few academic articles each year compared to more accessible fields. Though much has been achieved since the publication of two related volumes earlier in this series: Positron Solid State Physics (1981) and Positron Spectroscopy of Solids (1993), only the first steps have been made towards 'physics with many positrons': physical situations where the interactions of positrons with positrons can be observed. This 2009 "Enrico Fermi School" aims to stimulate the field o.

The NATO Advanced Research Workshop on Atomic Physics with Positrons, which was held at University College London during 15-18 July 1987, was the fourth meeting in a series devoted to the general theme of positron colli sions in gases. Previous meetings have been held at York University, Toronto (1981); Royal Holloway College, Egham (1983) and Wayne State Uni versity, Detroit (1985). Recent very significant improvements in positron beam currents, due to the development of more efficient moderators and the use of more intense positron sources, are making possible an increasingly sophisticated range of experiments in atomic collision physics. Whereas a few years ago only total scattering cross sections could be determined, measurements can now be made of various partial and differential cross sections. Intense positron beams are also being used to produce positronium beams and already, as reported here, preliminary investigations have been made of collisions of positronium with several target systems. These experimental developments have stimulated, and been stimulated by, steady, if somewhat less spectacu1ar,progress in associated theoretical studies. Both aspects of the field are well represented in these Proceed ings.

With the termination of the physics program at PETRA, and with the start of TRISTAN and the SLC and later LEP, an era of e+e- physics has come to an end and a new one begins. The field is changing from a field of few specialists, to becoming one of the mainstream efforts of the high energy community. It seems appropriate at this moment to summarize what has been learned over the past years, in a way most useful to any high energy physicists, in particular to newcomers in the e+e- field. This is the purpose of the book. This book should be used as a reference for future workers in the field of e+e- interactions. It includes the most relevant data, parametrizations, theoretical background, and a chapter on detectors.

Positrons can be used to study metallic defects. Positron annihilation experiments have been carried out to identify the defects in complex oxides. Positrons have also been used to study the Bose–Einstein condensation (BEC). Ps-BEC can be used to measure antigravity using atomic interferometers. This Special Issue hopes to bring awareness of the various aspects of positron interactions to the larger physics communities. We invite authors to submit articles from all areas of physics.

This book provides a comprehensive summary of studies of the Z boson in electron positron interactions. The results that have been obtained have achieved unprecedented accuracy and have firmly established the Electroweak Standard Model as the cornerstone of our current understanding of modern particle physics. The book introduces the background to the Standard Model and the role of the Z boson and describes briefly the accelerators and experiments involved in these results. The five main chapters deal with the detailed measurements of the electroweak parameters of the Z, the study of QCD, heavy quark physics, tau lepton physics and the search for new particles. Each chapter ends with a summary and outlook to prospects of future accelerators. Most of the results are from the first six years running at the first phase of electron positron collider, LEP, at energies corresponding to the Z mass, but results from the SLAC Linear Collider and some new results at higher energies are also included.