|
The Omega baryons are a family of subatomic hadron particles that are represented by the symbol and are either neutral or have a +2, +1 or −1 elementary charge. They are baryons containing no up or down quarks.〔(【引用サイトリンク】Particle Data Group ">url=http://pdg.lbl.gov/2011/reviews/rpp2011-rev-naming-scheme-hadrons.pdf )〕 Omega baryons containing top quarks are not expected to be observed. This is because the Standard Model predicts the mean lifetime of top quarks to be roughly ,〔 〕 which is about a twentieth of the timescale for strong interactions, and therefore that they do not form hadrons. The first Omega baryon discovered was the , made of three strange quarks, in 1964.〔 〕 The discovery was a great triumph in the study of quark processes, since it was found only after its existence, mass, and decay products had been predicted in 1962 by the American physicist Murray Gell-Mann and, independently, by the Israeli physicist Yuval Ne'eman. Besides the , a charmed Omega particle () was discovered, in which a strange quark is replaced by a charm quark. The decays only via the weak interaction and has therefore a relatively long lifetime.〔 〕 Spin (''J'') and parity (''P'') values for unobserved baryons are predicted by the quark model.〔 〕 Since Omega baryons do not have any up or down quarks, they all have isospin 0. ==Omega baryons== † Particle (or quantity, i.e. spin) has neither been observed nor indicated. 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「Omega baryon」の詳細全文を読む スポンサード リンク
|