1.

A stationary positive pion disintergrated into a muon and n nertrino. Find the kinetic energy of the moun and the energy of the neutrino.

Answer»

Solution :Energy-momentum conservation implies
`O=vec(P)_(mu)+vec(pv)`
`m_(pi)c^(2)=E_(mu)+E_(v) or m_(pi)c^(2)-E_(v)=E_(mu)`
But `E_(v)=c|vec(p_(v))|=c|P_(mu)|`. THUS
`m_(pi)^(2)c^(4)-2m_(pi)c^(2).c|vec(p)_(mu)|+c^(2)p_(mu)^(2)=E_(mu)^(2)=c^(2)P_(mu)^(2)c^(4)`
Hence `c|vec(p_(mu))|=(m_(pi)^(2)-m_(mu)^(2))/(2m_(pi)).c^(2)`
Substituting `m_(pi)c^(2)= 139.6MeV`
`m_(mu)c^(2)= 105.7MeV` we GET
`T_(mu)= 4.12 MeV`
Also `E_(v)=(m_(pi)^(2)-m_(mu)^(2))/(2m_(pi))c^(2)= 29.8MeV`


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