Yup! It's so they can view what happens when these particles collide as the collisions happen, using specialized detectors. The ATLAS detector at CERN weighs 7,000 tons and is huge.

These reactions in the atmosphere happen very fast and are a bit chaotic. When a primary cosmic ray hits an atom in our atmosphere, it then sets off a chain reaction similar to billiard balls, resulting in "air showers", which are cascades of subatomic particles, such as hadrons, photons, muons, electrons, as well as ionized nuclei. The colliders allow physicists to view these kinds of reactions under controlled conditions right as the reactions happen, and can adjust things such as the energies. There's an array of detectors in Argentina which can detect the particles released by an air shower