10.2 Problems 55710.98 Sketch the Feynman diagrams and replace the symbolslwith the correct
leptons or anti-leptons in the following:
[University of Cambridge, Tripos 2004]
(i)l+n→e−+p
(ii)τ−→μ−+!+l ̄
(iii) B^0 →D−+μ++l
[The quark content ofB^0 isbd and D−iscd]
10.99 Draw the lowest order Feynman diagram for the following decays
(a)Δ^0 →pπ−
(b)Ω−→ΛK−
10.100 (a) Draw the lowest order Feynman diagram for e+e−→νμνμ
(b) Draw the lowest order Feynman diagram for D^0 →K−π+and estimate
the ratio of the transition rates.
[Quark contents (masses in MeV/c^2 ):Δ+=uud(1,232),Ω−=sss(1,672),
Ξ^0 =uss(1,315),p=uud(938),n=udd(940),π^0 =√^12[
uu+dd]
(135),
π+=ud(140),D^0 =cu(1,865),K−=us ̄ (494)]
[Adapted from University of Cambridge, Tripos 2004]
10.101 Draw the lowest order Feynman diagram for the following processes:
(a) e−−e−elastic scattering (Moller scattering)
(b) e+e−→e+e−(Bhabha scattering)10.102 Draw the lowest order Feynman diagram at the quark level for the following
decays
(a)Λ→p+e−+νe
(b)D−→K^0 +π−
10.103 Draw the Feynman diagrams at the quark level for the reactions:
(a)π−+p→K^0 +Λ
(b) e++e−→B^0 +B^0 , whereBis a meson containing a b-quark.
10.104 Draw the lowest order Feynman diagram for the decayK−→μ−+νμ+γ
and hence deduce the form of the overall effective coupling.
10.105 Explain with the aid of Feynman diagrams, why the decayD^0 →K−+π+
can occur as a charged-current weak interaction at lowest order, but the
decayD+→K^0 +π+cannot.
10.106 Why is the mean lifetime of the charged pion much longer than that of the
neutral pion? Draw Feynman diagram to illustrate your answer.
10.107 Draw Feynman diagrams for
(a) Bremsstrahlung
(b) pair production.
10.108 Draw Feynman diagrams for
(a) photo electric effect
(b) Compton scattering