Also found in: Dictionary, Thesaurus, Wikipedia.
J particle[′jā ‚pärd·ə·kəl]
A neutral meson which has a mass of 3095 megaelectronvolts, spin quantum number 1, and negative parity and charge parity; it has an anomalously long lifetime of approximately 10-20 second (corresponding to a width of approximately 70 kiloelectronvolts). Also known as psi particle (symbolized ψ).
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.