In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: π^0, π^+ and π^−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. Basic properties Pions have zero spin and are composed of first-generation quarks. In the quark model, an up and an anti-down quark compose a π^+, while a down and an anti-up quark compose the π^−, its antiparticle. The neutral combinations of up with anti-up and down with anti-down have identical quantum numbers, so they are only found in superposition. The lowest-energy superposition is the π^0, which is its own antiparticle. Together, the pions form a triplet of isospin; each pion has isospin-1 (I = 1) and third-component isospin equal to its charge (Iz =&nbs

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