pion (pī´ŏn) or pi meson, lightest of the meson family of elementary particles. The existence of the pion was predicted in 1935 by Hideki Yukawa, who theorized that it was responsible for the force of the strong interactions holding the atomic nucleus together. It was first detected in cosmic rays by C. F. Powell in 1947. The pion is actually a multiplet of three particles. The neutral pion, π0, has a mass about 264 times that of the electron. The charged pions, π+ and π-, each have a mass about 273 times that of the electron. The neutral pion is its own antiparticle, while the negative pion is the antiparticle of the positive pion. It is now known that each pion (and, more generally, each meson) consists of a quark bound to an antiquark. Free pions are unstable. The charged pions decay with an average lifetime of 2.55 × 10-8 sec into a muon of like charge and a neutrino or antineutrino; the neutral pion decays in about 10-15 sec, usually into a pair of photons but occasionally into a positron-electron pair and a photon.
"pion." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (December 17, 2018). https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/pion
"pion." The Columbia Encyclopedia, 6th ed.. . Retrieved December 17, 2018 from Encyclopedia.com: https://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/pion
Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).
Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:
Modern Language Association
The Chicago Manual of Style
American Psychological Association
- Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
- In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.