Mesons

Mesons

Mesons of spin 0 form a
Composition	Composite—Quarks and antiquarks
Statistics	Bosonic
Interactions	Strong, Weak, Electromagnetic and Gravity
Theorized	Hideki Yukawa (1935)
Discovered	1947
Types	~140 (List)
Mass	From 134.9 MeV/c2 ( π0 ) to 9.460 GeV/c2 ( ϒ )
Electric charge	−1 e, 0 e, +1 e
Spin	0, 1

In particle physics, mesons (/ˈmiːzɒnz/ or /ˈmɛzɒnz/) are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of quark sub-particles, they have a physical size, with a diameter of roughly one fermi, which is about  ²⁄₃ the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through mediating particles) to form electrons and neutrinos. Uncharged mesons may decay to photons. Both of these decays imply that color is no longer a property of the byproducts.

Outside of the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays (high energy protons and neutrons) and ordinary matter. Mesons are also frequently produced artificially in high-energy particle accelerators in the collisions of protons, anti-protons, or other particles.