Final answer:
In an electron-proton collision, the exchange particle is the photon, which mediates the electromagnetic force. High-energy collisions at particle accelerators like the LHC may observe other exchange particles, but for simple electron-proton interactions, the photon is key.
Step-by-step explanation:
The exchange particle involved in an electron-proton collision is primarily the photon. In the realm of quantum electrodynamics (QED), which describes how light and matter interact, photons act as force carriers for the electromagnetic force. During a scattering event such as an electron-proton collision, photons are exchanged between the particles, resulting in electromagnetic interaction. It's quite different from a scenario where particles like protons and neutrons interact via the strong force, where particles such as pions or gluons would be the exchange particles.
Colliding particles at high energies, as done in facilities like the Large Hadron Collider (LHC), can create conditions where other exchange particles might be observed. For an electron-proton collision, the strong force is not typically involved, and hence pions are not expected as exchange particles. Instead, the higher-energy collisions of protons at places like the LHC might reveal more about the strong force exchange particles like gluons or even hint at new physics by possibly discovering particles like the Higgs boson.