Pions, or pi mesons, are subatomic particles that are important in the interactions between nucleons in atomic nuclei. They are the lightest mesons and come in three varieties: positively charged, negatively charged, and neutral. These particles play a key role in mediating the strong nuclear force, which binds protons and neutrons together within the nucleus, making them essential in the context of relativistic quantum mechanics and the Klein-Gordon equation.
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