# J/psi particle

> English word · Noun · IPA /ˌdʒeɪ ˈsaɪ ˈpɑːtɪkl̩/

## Definitions
1. A subatomic particle with an unusually long lifetime (7.2 × 10⁻²¹ s) and a large mass (approx. 3.097 GeV/c²); a bound state of a charm quark and an anti-charm quark (the most common form of charmonium).

## Etymology
A compound of J, ψ (psi), and particle. The particle was discovered independently in 1974 by two research groups, leading to the "November Revolution" in particle physics.
* The group led by Samuel Ting at Brookhaven National Laboratory proposed the name J, reputedly because the shape of the Chinese character for Ting (丁) resembles a J, though Ting also cited the symbol for electromagnetic current, j_μ(x), as a reason.
* The group led by Burton Richter at SLAC proposed the name ψ (psi). Richter initially preferred "SP" (for the SPEAR accelerator), but chose "psi" as it contained "SP" in reverse order and was the only remaining Greek letter deemed suitable; coincidently, the particle's decay pattern in spark chambers resembled the letter ψ.
The compromise name J/ψ was adopted to acknowledge both discoveries.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/j-psi-particle