Scientists chose to use protons as particles in colliders for several practical reasons:
Abundance: Protons are the most abundant particles in the universe. They are present in the nuclei of all ordinary matter, including atoms. This abundance makes protons easily accessible and cost-effective for use in colliders.
Stability: Protons are relatively stable particles, meaning they have long lifetimes. This stability allows them to be accelerated to high energies and collide with other particles without decaying prematurely. More exotic particles, such as kaons or pions, have shorter lifetimes and are more challenging to handle in colliders.
Energy Efficiency: Protons are electrically charged particles, and their acceleration can be achieved using electric fields. Electrically charged particles are more easily controlled and manipulated using electromagnetic fields than neutral particles like kaons or pions. This makes proton accelerators more efficient in terms of energy transfer and beam control.
Interaction Cross-section: Protons have a relatively large interaction cross-section, which means they are more likely to collide and interact with other particles. This high interaction probability increases the chances of producing interesting and rare phenomena during collisions.
Well-understood Interactions: The interactions of protons are well-studied and understood due to their prevalence in nature. Proton-proton collisions have been extensively studied, and the theoretical models for their interactions are well-developed. This knowledge facilitates the interpretation of experimental data and the comparison with theoretical predictions.
While protons are the most commonly used particles in colliders, scientists do study collisions involving other particles, such as kaons, pions, electrons, or heavy ions, depending on the specific goals and objectives of their experiments. Each choice of particle brings unique advantages and challenges, and the selection depends on the scientific questions being addressed and the capabilities of the accelerator facilities.