Eur. Phys. J. D 29, 321-327 (2004)
https://doi.org/10.1140/epjd/e2004-00052-0

A new ab initio method of calculating and positron annihilation rates using coupled-channel T-matrix amplitudes

Departamento de Física, Instituto Tecnológico de Aeronáutica, CTA São José dos Campos 12228-901, SP, Brasil and Divisão de Engenharia Biomédica, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, São José dos Campos 12244-000, SP, Brasil

Corresponding author: ^a biswas@fis.ita.br

Received: 28 July 2003
Revised: 15 January 2004
Published online: 15 April 2004

Abstract

We present a new ab initio theoretical formulation to calculate and hence the positron annihilation rates directly from the onshell and offshell (half) scattering amplitudes. The method does not require any explicit use of the scattering wave function and is formally exact within the framework of the well established Lippmann-Schwinger equation. It could serve as an effective tool as all the T-, K-, and S-matrix formulations, yield directly the scattering amplitudes; not the wave function. Numerical test of the method is presented considering sample static calculations in positron-hydrogen and positron-helium systems.