[yoop-suh-lon, -luh
n, uhp-; especially Brit. yoop-sahy-luhn] 
| 1. | the 20th letter of the Greek alphabet (Υ, υ). |
| 2. | the vowel sound represented by this letter. |
| 3. | Also called upsilon particle. Physics. any of a family of heavy, short-lived, neutral mesons that are composed of a bottom quark and its antiquark. Symbol: Υ, υ |
| upsilon particle n. An electrically neutral meson having a mass 18,513 times that of the electron and a mean lifetime of approximately 8.0 × 10-20 seconds. See Table at subatomic particle. |
upsilon up·si·lon or yp·si·lon (ŭp'sə-lŏn', y&oomacr;p'-)
n.
Symbol υ The 20th letter of the Greek alphabet.
upsilon particle (ŭp'sə-lŏn', y p'-) Pronunciation Key
An electrically neutral meson having a mass 18,513 times that of the electron and a mean lifetime of approximately 8.0 × 10-20 seconds. See Table at subatomic particle. |