Feynman Diagrams For Pedestrians - Herbstschule Maria Laach

6 Standard Model(C, T) Y Q = T 3 + Y 2leptonsν e,R ν µ,R ν τ,R (1, 1) 0 0e R ) (µ R ) (τ R )(1, 1) −2 (− 1)νµ,L ντ,L0(1, 2)e L µ L τ −1L −1(νe,Lquarks2u R c R t R (3, 1) 4/3 3d R) (s R) (b R)(3, 1) −2/3(− 1 3 2)cL tL(3, 2)3d L s L b 1/3L − 1 3(uLgauge bosonsA Z 0 W ± gHiggsΦ (1, ?) ? ?6.1 Propagators• external spin-1 particlesincoming:outgoing:kk⇐⇒ ɛ µ (k)⇐⇒ ɛ ∗ µ(k)(169a)(169b)• internal particles and anti particlesSpin-1 (m 0):k⇐⇒ −ig µν + i k µk νM 2k 2 − M 2 + iΓM(170)• polarization sum:∑pol.ɛ µ (k)ɛ ∗ ν(k) = −g µν + k µk νM 2 (171)• unitarity gauge: ∂ µ D µν = 0, other options−ig µν + i(1 − ξ) k µk νk 2 −ξM 2k 2 − M 2 + iΓMbetter for radiative corrections, but larger intermediate terms(172)• finite width Γ: (tricky for charged particles, but required)|D(p, M)| 2 ∝1(p 2 − M 2 ) 2 + Γ 2 M 2 (173)35