A unified theory of electromagnetic and weak interactions proposed separately by Steven Weinberg in 1967 and Abdus Salam in 1968. It is a quantum field theory of renormalizable (non-Abelian) gauge fields that describes the two interactions in a unified manner by introducing two types of charged vector mesons W + and W - and two types of neutral vector mesons as gauge bosons. Neutral mesons mix in a certain ratio to become the massless photon that mediates the electromagnetic interaction with the very heavy meson Z, and Z mesons are considered to mediate the weak interaction together with the charged mesons W + and W - . The three gauge bosons other than the photon acquire mass through the Higgs mechanism. The mass of the W meson was predicted to be 3.8×10 4 /sinθ W MeV (megaelectronvolts), and the mass of the Z meson was predicted to be 7.6×10 4 /sin2θ W MeV. Here, θ W is a quantity that represents the mixing ratio of neutral mesons and is called the Weinberg angle. Analysis of high-energy neutrino experiments gives sin 2 θ W = 0.2315 ± 0.0005. In 1983, W + , W - and Z 0 were discovered at CERN (European Organization for Nuclear Research) with masses exactly as predicted by the theory. Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information |
1967年にスティーブン・ワインバーグが,1968年にアブドゥス・サラムが個別に提案した電磁相互作用と弱い相互作用の統一理論。2種類の荷電ベクトル中間子 W+,W-と 2種類の中性ベクトル中間子をゲージボソンとして導入することにより,二つの相互作用を統一的に記述するくりこみ可能な(非可換)ゲージ場の場の量子論。中性中間子は一定の割合で混合して非常に重い中間子 Zと電磁相互作用を媒介するゼロ質量の光子となり,Z中間子は荷電中間子 W+,W-とともに弱い相互作用を媒介するとみなされる。光子以外の 3種のゲージボソンはヒッグス機構により質量を獲得する。W中間子の質量は 3.8×104/sinθWMeV(メガ電子ボルト),Z中間子の質量は 7.6×104/sin2θWMeVと予言された。ただし,θWは中性中間子の混合比を表す量で,ワインバーグ角と呼ばれる。高エネルギーのニュートリノ実験の分析によれば sin2θW=0.2315±0.0005である。1983年ヨーロッパ原子核研究機関 CERNで W+,W-および Z0が理論の予言どおりの質量で発見された。
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