pion

[ pahy-on ]

noun

, Physics.

1. the first meson to be discovered: it has spin 0 and may be positively or negatively charged or neutral; charged pions decay into a muon and a neutrino or antineutrino. : π

pion

/ ˈpaɪɒn /

noun

1. physics a meson having a positive or negative charge and a rest mass 273.13 times that of the electron, or no charge and a rest mass 264.14 times that of the electron

pion

/ pī′ŏn′ /

1. A meson occurring either in a neutral form with a mass 264 times that of an electron and a mean lifetime of 8.4 × 10 ^-17 seconds or in a positively or negatively charged form with a mass 273 times that of an electron and a mean lifetime of 2.6 × 10 ^-8 seconds. The pion was once believed to be the particle that mediates the strong force , which holds nucleons together in the nucleus; it is now believed that the gluon is the mediator particle. Pions do interact with nucleons, however, and are able to transform neutrons into protons and vice versa.
2. Also called pi-meson
3. See Table at subatomic particle

Word History and Origins

Origin of pion¹

First recorded in 1950–55; pi (meson) + -on ¹

Word History and Origins

Origin of pion¹

C20: from Greek letter pi ¹+ on

Example Sentences

They had already found the pion for which Prof Powell would be awarded the Nobel Prize in 1950.

From BBC

They would fire a proton beam into a target to produce particles called charged pions, which, swirling in a magnetic field, would decay into muons.

From Science Magazine

Neutrinos can be formed when the high-energy radiation that makes up most cosmic rays interacts with matter, creating charged particles called pions, which produce neutrinos as they decay.

From Scientific American

The positive pion can interfere with other positive pions caused by other atomic flybys.

From Scientific American

Protons and neutrons stick together by exchanging particles called pions, and a quantum mechanical effect favors nuclei with similar numbers of protons and neutrons.

From Science Magazine