## Friday, December 16, 2011

### 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+0

K+→μ+μ

K+→π++0

K+→π+00

K+→e++ν+π0

• Mass of K+ is 966me.
• 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