Mesons

• Mesons are particles with zero or integral spin so they are Bosons.
• The lightest meson is pion or π-meson, with other meson masses ranging beyond proton mass.
• All mesons are unstable and decays in various ways.

π-mesons

• This particle is to transmit nuclear forces, it must interact strongly with nuclei, and therefore it should be scattered and absorbed quickly by matter through which it passes.
• π mesons are thus hypothetical particles responsible for the nuclear forces and had properties pridicted by Yukawa.
• Protons and neurtons can be transferred into one anotherby emitting or absorbing one of these particles.
• There are three kinds of pions π⁺, π^- and π⁰. π^- is the anti particle of π⁺.
• These new particles can be thought of making bonds between (n,n) , (p,p) and (n,p) or (p,n)

K mesons

• These are heavier unstable particles and have a great variety of different decay modes.
• THere are six different ways that K⁺ mesons commonly decay, in each case giving two or three less massive particles

  K⁺→π⁺+π⁰

  K⁺→μ⁺+ν_μ

  K⁺→π⁺+π⁺+π⁰

  K⁺→π⁺+π⁰+π⁰

  K⁺→e⁺+ν+π⁰

• Mass of K⁺ is 966m_e.
• K^- are anti particles of K⁺ mesons and have the same decay modes with appropriate exchange of decay products for their anti particles.
• K⁰ and $\overline{K^0}$are anti particles.

Mesons (B=0) Bosons

Particle	Symbol	Mass MeV/c2	Mean life (s)	spin	S	Y	I	I3
Pion	π+	140	2.6×10-8	0	0	0	1	+1
	π0	135	8.7×10-17					0
	π-	140	2.6×10-8					-1
Kon	K+	494	1.2×10-8	0	+1	+1	1/2	+1/2
	K0	498	9×10-11
	K-	494	5×10-8					-1/2
Eta	η0	549	6×10-19	0	0	0	0	0