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pion 音标拼音: [p'ɑɪ ,ɑn] n. ｋ介子 ｋ介子 pion n 1: a meson involved in holding the nucleus together; produced as the result of high- energy particle collision [ synonym: { pion}, { pi- meson}] Meson \ Mes" on\, n. [ NL., fr. Gr. me` son middle, neut. of me` sos, a., middle.] 1. ( Anat.) The mesial plane dividing the body of an animal into similar right and left halves. The line in which it meets the dorsal surface has been called the dorsimeson, and the corresponding ventral edge the ventrimeson. -- B. G. Wilder. [ 1913 Webster] 2. ( Physics) An elementary particle made up of two quarks; a hadron having a baryon number of zero; any hadron other than a baryon. Mesons are bosons with integral values of spin, having a mass intermediate between those of the electron and a nucleon; they may have positive or negative charges, or may be neutral. Mesons are of three types: the { pion} ([ pi]- meson), { kaon} ( K- mesons), and {[ eta]- mesons}. [ PJC] { mu meson} ( Physics) the former name for the { muon}, a particle which is not a true meson[ 2]. The term is no longer used in technical literature, except historically. [ PJC]
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