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Physicist believe there are six quarks - up (u), down (d), charm (c), strange (s), top (t), and bottom (b) and their antiquarks - antiup, antidown, anticharm, antistrange, antibottom, and antitop. Antiquarks are labeled with a letter with a bar over it. |
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Each meson consists of one quarks and one antiquark represented by small circles within the larger circle. Quarks are labeled with a letter. A meson cannot be made of two quarks or two antiquarks. |
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Examples of mesons are the pion and the kaon. |