Chapter 46621Q46.18The Ξ−particle has, from Table 46.2, charge –e, spin 12, B=1, LL Le===µτ0, and strangeness –2.All of these are described by its quark composition dss (Table 46.5). The properties of the quarksfrom Table 46.3 let us add up charge: −−−=−131313eeee; spin +−+=12121212, supposing one of thequarks is spin-down relative to the other two; baryon number 1313131++=; lepton numbers, charm,bottomness, and topness zero; and strangeness 0 1 12−−=−.Q46.19The electroweak theory of Glashow, Salam, and Weinberg predicted the W+, W−, and Z particles.Their discovery in 1983 confirmed the electroweak theory.Q46.20Hubble determined experimentally that all galaxies outside the Local Group are moving away fromus, with speed directly proportional to the distance of the galaxy from us.Q46.21Before that time, the Universe was too hot for the electrons to remain in any sort of stable orbitaround protons. The thermal motion of both protons and electrons was too rapid for them to be inclose enough proximity for the Coulomb force to dominate.
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