| 单词 | sigma particle |
| 释义 | sigma particle A type of spin ½ baryon. There are three types of sigma particles, denoted Σ-, Σ0, Σ+, for the negatively charged, electrically neutral, and positively charged forms, respectively. The quark content of the sigma particles are Σ- (dds), Σ0 (dus), Σ+ (uus), where d, u, and s denote down, up, and strange, respectively. The masses of the sigma particles are 1189.36 MeV (Σ+), 1192.46 MeV (Σ0), 1197.34 MeV (Σ-); their average lifetimes are 0.8 × 10-10 s (Σ+), 5.8 × 10-20 s (Σ0), and 1.5 × 10-10 s (Σ-) |
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