A boson notated with this letter is the weak hypercharge gauge boson and can mix with W3 to form the Z boson and photon. A set (15[1])of four mesons symbolized by this letter includes the heaviest [emphasize] charged meson, as well as the heaviest neutral mesons to undergo matter-antimatter oscillations. A quantum number represented by this letter equals one-third of the quantity number of quarks minus the number of antiquarks, and is conserved in the Standard Model along with (*) L. The upsilon meson is made up of a quark of this letter paired with its antiquark. Yellow is the anticolor of this color state, the alphabetically first of (10[1])three. This letter represents the second-heaviest quark, which is paired with the top quark in the third generation. For 10 points, name this letter which, along with r and g, constitutes color charge. (10[1])■END■