The mass of these particles is related to the masses of two smaller particles by the GMOR, or Gell-Mann–Oakes–Renner relation. A Lagrangian that is invariant under S·U-two cross S·U-two canonically contains a term normalized by f squared over 4, where f is a constant named for these particles. The strength of the spontaneous breaking of chiral symmetry in QCD is related to this particle’s “decay constant.” The theoretical decay of the phi meson into three of these particles is suppressed per the (*) OZI rule. (10[1]-5[2])The paper that originally (-5[1])proposed this particle derived its existence from a potential (10[1])given by an exponential screening term, times a typical “one over (10[1])r” Coulomb potential. Hideki Yukawa proposed that this particle (10[1])mediates the strong force between (-5[1])nucleons. (-5[1])For 10 points, an up or down quark bound to an up or down antiquark comprises what lightest meson? ■END■ (10[3]0[2])