Final answer:
Protons are baryons, which are particles made up of three quarks. In contrast, photons are elementary particles associated with electromagnetic radiation and are not baryons. Electrons, involved in the discovery of quarks, are leptons, another category of fundamental particles.
Step-by-step explanation:
Among the options provided, protons are baryons. Baryons are composite subatomic particles made up of three quarks and are part of the hadron family. Examples of baryons include protons and neutrons, found within the nucleus of an atom. In contrast, photons are not baryons; they are elementary particles that are the quantum of the electromagnetic field, including electromagnetic radiation such as light, and are responsible for electromagnetic force.
In the original discovery of the quark, electrons were the particles launched into the proton. The highly energetic photons inside protons are not related to the particles' baryonic nature but contribute to the proton's internal mass compared to electrons through the strong force. During transitions from excited states to the ground state, a proton emits photons of specific energies. It is essential to note that photons and electrons are both fundamental particles with electrons being leptons, not hadrons or baryons.
To summarize, protons are examples of baryons, whereas photons are not. This distinction reflects the fundamental organization of particles in the Standard Model of particle physics.