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, | composition = }} }} | statistics = Bosonic | group = Mesons | generation = | interaction = Strong, Weak, Gravitation | antiparticle = Self | theorized = | discovered = | symbol = , | mass = 〔 〔 | decay_particle = : or : | electric_charge = | color_charge = | spin = Integer | num_spin_states = }} The eta () and eta prime meson () are mesons made of a mixture of up, down and strange quarks and their antiquarks. The charmed eta meson () and bottom eta meson () are forms of quarkonium; they have the same spin and parity as the light eta but are made of charm quarks and bottom quarks respectively. The top quark is too heavy to form a similar meson, due to its very fast decay. ==General== The eta was discovered in pion-nucleon collisions at the Bevatron in 1961 by A. Pevsner et al. at a time when the proposal of the Eightfold Way was leading to predictions and discoveries of new particles from symmetry considerations.〔 The difference between the mass of the ''η'' and that of the ''η is larger than the quark model can naturally explain. This "η-η' puzzle" can be resolved〔〔〔 by the 't Hooft instanton mechanism,〔 whose 1/N realization is also known as Witten-Veneziano mechanism.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eta meson」の詳細全文を読む スポンサード リンク
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