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J/psi meson(jā′sī′, -psī′)
An electrically neutral meson containing a charm quark and a charm antiquark having a mass about 6,060 times that of the electron and a mean lifetime of approximately 7.2 × 10-21 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.