10.3 Solutions 601
where the combinations (1,2) are (e+,νe)or(μ+,νμ)or(d ̄,u), the last
one three times for three colors. The combinations (τ+,ντ) and ( ̄s,c)are
ruled out as energy is violated.
(b) Hadronic decay ofτ−
τ−→π−ντFig. 10.29(b)
10.112 (a)
Fig. 10.30(a)
Two-photon annihilation; two ordered diagrams
(b)Fig. 10.30(b)