Exploring the universe with Ultra High Energy Cosmic Rays

The most energetic particles ever detected present a long standing puzzle in the fields of both astro- and particle physics. With energies of up to 10 million times higher than those produced in the large hadron collider at CERN, these particles are believed to be created in violent astrophysical events before travelling vast distances through extragalactic space to reach us here on Earth. Along with other astrophysical messengers, gamma-rays and neutrinos, UHECR allow us to study the properties of their sources and the medium through which they travel. However, little is known about the details of the phenomenology and it is challenging to build models which can accelerate particles to such high energies under multi-messenger constraints. To make matters worse, UHECR are so rare that they can only be detected indirectly by using the Earth's atmosphere as a giant calorimeter. Research here at KTH focuses on the development of a space-based UHECR observatory as part of the EUSO collaboration, and the data analysis of existing events to investigate potential UHECR sources. The goal in both cases is to improve our understanding of where UHECR originate and their acceleration mechanisms.