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The pion may be positively or negatively charged, or neutral. Positive
and negative pions decay with an average lifetime of 26 billionths of
a second. Neutral pions, however, decay in 84 billion billionths of a
second.
As shown below, a negative pion produces a negatively
charged muon and the muon's antineutrino.
In about two millionths of a second, the muon breaks up into an
electron and two neutrinos. The pions, muons or protons can be used
as probes of subatomic matter.
By shooting a proton beam into various metallic target materials, a subatomic research lab like TRIUMF can, every second, produce billions of unusual subatomic particles called pions. Some are electrically neutral, others carry a negative or a positive charge. They are all classed as "mesons". |
| Discovered: | 1947 |
| Electric charge: | -1 (same as an electron> |
| Mass: | 1/7 of a proton (or 273 electron-masses) |
| Compositon: | One "down" quark + one "up" antiquark |
| Average lifetime: | 26 billionths of a second |
| Decays into: | In a vacuum, usually a negative muon, and an antineutrino. However, the antimatter in a pion makes it very unstable - if a negative pion is captured by a (positively charged) nucleus of an atom, the pion's entire mass can often be converted into pure energy, making the nucleus explode like a tiny atomic bomb! |
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Last changes: Jan 02, 1997. |