Determinação das seções de choque elásticas para colisões de pósitrons com as moléculas de N2, O2 e CO2 com a correção para o espalhamento em baixo ângulo

Abstract

The study of matter-antimatter interactions began with the detection of the positron. Despite considerable progress in this field, challenges remain in achieving complete agreement between theory and experiment, particularly at low energies where the low-angle scattering problem persists. This dissertation aims to determine the cross sections for elastic collisions of positrons with N2, O2, and CO2 molecules, proposing a correction for the experimental measurements affected by low angle scattering effect. To describe the positron-molecule interaction, we use a scattering model potential that includes polarizabilities beyond dipole, combined with the Method of Continued Fractions to solve the scattering equations. After the determination of cross sections, we conduct a historical literature review on positron impact scattering experiments, characterizing the forward scattering effect and proposing a correction methodology. The results suggest that theoretical calculations incorporating additional terms from the perturbative series in the interaction potential exhibit improved convergence with corrected experimental data. These adjustments enable a fair comparison between cross sections and allow for a detailed analysis of the role of correlation and polarization effects in positron scattering dynamics with molecules, contributing to a more accurate comparison of matter-antimatter interactions.