Vertex Reconstruction with Silicon Pixel Detectors for Studying Antiproton-Nucleus Annihilation

A number of experiments at CERN’s Antiproton Decelerator aim to measure the properties of antihydrogen to find structural differences hinting at CPT symmetry breaking that would explain the observed baryon-antibaryon asymmetry in our universe. These experiments detect antimatter through its annihilation, making the antiproton-nucleus (pbarA) interaction one of the main processes of interest. As the mechanism itself is not yet fully understood, the ASACUSA-Cusp collaboration will study the pbarA annihilation at rest on a variety of nuclei using thin target foils. Surrounding these foils a novel detection system using Timepix4 hybrid pixel detectors with silicon sensors that will cover most of the solid angle is being designed to measure the total multiplicities of prongs and their kinetic energies. Particle identification methods using the deposited energy and data cluster morphology will be deployed to identify minimum and heavily ionizing particles. To precisely tag individual events, an algorithm for 3D reconstruction of the annihilation vertices is developed by extrapolating the recorded particle tracks in the single-plane detectors. This will also reveal the angular distribution of the prongs. This experiment will allow studying the possible final state interactions triggered by the primary annihilation mesons as well as their branching ratios. Its results will be implemented for assessment of simulation models such as the Liège Intranuclear Cascade model.