Related to eta-c meson: eta prime meson
e·ta-c meson(ā′tə-sē′, ē′tə-)
An electrically neutral meson composed of a charm quark and a charm antiquark and having a mass 5,832 times that of the electron and a mean lifetime of about 2.6 × 10-23 second.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.