Pions do not directly hold quarks close together. The strong nuclear force, mediated by gluons, is the fundamental force responsible for binding quarks within particles like protons and neutrons.
Pions, on the other hand, are mesons composed of a quark and an antiquark pair. They are formed by the exchange of gluons between quarks. The strong force, carried by gluons, acts between the quarks inside the pion and binds them together.
The strong force is unique among the fundamental forces in that it becomes stronger as the distance between quarks increases. This phenomenon is called confinement. As quarks separate, the energy stored in the strong force field between them increases, making it more energetically favorable for new quark-antiquark pairs to form, rather than having isolated quarks.
The strong force binds quarks together within particles, creating a phenomenon known as color confinement. Quarks are never observed as isolated particles in nature due to this confinement. Instead, they are always found in groups or combinations within color-neutral composite particles like pions, protons, and neutrons.
While pions themselves do not directly hold quarks close, they are mesons that arise from the strong force interaction between quarks, and their existence is a result of the strong force's role in binding quarks together.