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R-parity is a concept in particle physics. In the Minimal Supersymmetric Standard Model, baryon number and lepton number are no longer conserved by all of the renormalizable couplings in the theory. Since baryon number and lepton number conservation have been tested very precisely, these couplings need to be very small in order not to be in conflict with experimental data. R-parity is a symmetry acting on the Minimal Supersymmetric Standard Model (MSSM) fields that forbids these couplings and can be defined as〔 〕 : or, equivalently, as : where ''s'' is spin, ''B'' is baryon number, and ''L'' is lepton number. All Standard Model particles have R-parity of +1 while supersymmetric particles have R-parity of −1. ==Dark matter candidate== With R-parity being preserved, the lightest supersymmetric particle (LSP) cannot decay. This lightest particle (if it exists) may therefore account for the observed missing mass of the universe that is generally called dark matter. In order to fit observations, it is assumed that this particle has a mass of to , is neutral and only interacts through weak interactions and gravitational interactions. It is often called a weakly interacting massive particle or WIMP. Typically the dark matter candidate of the MSSM is an admixture of the electroweak gauginos and Higgsinos and is called a neutralino. In extensions to the MSSM it is possible to have a sneutrino be the dark matter candidate. Another possibility is the gravitino, which only interacts via gravitational interactions and does not require strict R-parity. 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「R-parity」の詳細全文を読む スポンサード リンク
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