Positron Physics in a New Perspective

Abstract

A large group of experimentalists is currently working on the preparation of the ATHENA (ApparaTus for High precision Experiments on Neutral Antimatter), which is to be used at CERN to carry out experiments on antihydrogen to test the CPT invariance of Quantum Field Theory and also Einstein's Principle of Equivalence. It is intended to carry out these experiments by trapping at very low temperatures ( < 1 K ) in an inhomogeneous magnetic field. The size and extent of the collaboration on this project can be seen from ref. [14], which is entitled 'Antihydrogen production and precision experiments' and has 54 authors from 7 different countries.In this chapter, we consider some of the interesting theoretical problems that arise when in which a positron is bound to an antiproton, interacts with H, He andThe theoretical work that has been carried out for is described. This includes a very recent preliminary calculation that we have carried out using the Kohn variational method. Methods of extending this work to scattering by He and are discussed. These processes are the main cause of loss of trapped Thus there is considerable interest in obtaining cross sections for them, in order to determine annihilation rates under various experimental conditions. The aim is to make it possible for experimentalists to choose the conditions which maximise the lifetime of the 53

Calculation of cross sections for very low-energy hydrogen antihydrogen scattering using the Kohn variational method

“…The radial part of φ B O , χ(R), makes allowance for the dominance of the Coulombic potential when the nuclei are close together and takes into account the van der Waals nature of the potential when H and H are far apart. The complicated nature of the Kohn calculation made it impossible to use as large a basis set in calculating the BO leptonic wavefunction and associated potential as in our earlier BO calculation [17]. However, this BO potential was very close in value to the potential obtained in this earlier calculation.…”

“…Some calculations were performed on the hydrogen-antihydrogen (H-H) system in the period up until 1997 (see, for example, [1][2][3][4][5]). However, experimental work with the aim of producing very cold, trapped antihydrogen ( H) [6][7][8][9], is currently being carried out on two projects, ApparaTus for High precision Experiments on Neutral Antimatter (ATHENA) and Antihydrogen TRAP (ATRAP), and this has generated much greater theoretical interest in this system [10][11][12][13][14][15][16][17][18][19][20]. Very recently, experimentalists on the ATHENA project have succeeded in preparing about 50 000 H atoms, cooled to within 15 • of absolute zero [21].…”

“…We also computed a very accurate Born-Oppenheimer (BO) potential for H-H and used it to calculate an s-wave nuclear scattering wavefunction and associated phase shifts. Details of these preliminary calculations are given in [17,22].…”

Stability of few-charge systems in quantum mechanics

“…However, the work on the preparation of H described above has generated greater theoretical interest in this system, Armour et al [169,211,212,213,214,215] Jonsell, Froelich et al [216,217,218,219,220,221,222], Sinha and Ghosh [223], Voronin and Carbonell [224].…”