upsilon particle

American  

noun

plural

upsilon particles

1. Physics. a meson with a neutral charge, a mass 18,513 times that of the electron and a mean lifetime of approximately 8.0 × 10^-20 seconds.

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upsilon particle Scientific  

/ ŭp′sə-lŏn′,yo̅o̅p′- /

1. 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.

2. See Table at subatomic particle

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