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10 Particle Physics – II
10.109 Draw Feynman diagrams for the processes
(a) e
+ e
−
→ qq
(b) ν μ + N → ν μ + X .
10.110 Draw Feynman diagrams for the decays
(a) Ξ
−
→ Λ + π
−
(b) K
+
→ π
+
π
+
π
−
10.111 (a) Draw the Feynman diagram for the semi leptonic decay of D
+
→ K
0
+
l + ¯
l.
(b) Draw Feynman diagram for the tauon decay τ
−
→ π
−
+ ν τ
10.112 Draw Feynman diagrams for (a) Two-photon annihilation (b) Three-photon
annihilation of positronium.
10.113 Draw the Feynman diagram for the decay Λ → p + π
−
10.3 Solutions
10.3.1 Conservation Laws
10.1 (i) Weak decay
Fig. 10.2(a)
(ii) Forbidden because Baryon number is violated
(iii) Charge current weak interaction
Fig. 10.2(b)
(iv) Forbidden because energy is not conserved