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K meson[′kā ¦mā‚sän]
Collective name for four pseudo-scalar mesons, having masses of about 495 MeV (megaelectronvolts) and decaying via weak interactions: K +, K -, K 0S, and K 0L; they consist of two isotopic spin doublets, the (K +, K 0) doublet and its antiparticle doublet (K -, K̄ 0), having hypercharge or strangeness of +1 and -1 respectively, where K 0 and K̄ 0 are certain combinations of KL 0 and KS 0 states. Also known as kaon.
Collective name for any meson resonance belonging to an isotopic doublet with hypercharge +1 or -1, denoted KJP (m) or K̄JP (m) respectively, where m is the mass in megaelectronvolts, and J and P are the spin and parity.