Feynman Diagrams For Pedestrians - Herbstschule Maria Laach

x 210.80.60.40.2x 3 = 100 0.2 0.4 0.6 0.8 1x 1x 3 = 0• for massless particles∑spins, pol.∫d ˜Ω |T 1 + T 2 | 2 = 4e4 g 2 Q 2×( pµ p νss 2 (p µ 1 pν 2 + p ν 1 p µ 2 − p 1p 2 g µν )− g µν)˜H(p, x 1 , x 2 ) = 4e4 g 2 Q 2s˜H(p, x 1 , x 2 ) (166)• add phase space factord 2 σ= 1 s 1dx 1 dx 2 2s 128π 3 4∑∫d ˜Ω |T 1 + T 2 | 2 = α sα 2 Q 2spins, pol.4s˜H(p, x 1 , x 2 ) (167)Problem 22. Express the invariants q 1 q 2 , q 1 k and q 2 k by s and the x i , assuming all particlesto be massless.Problem 23. Computefor massless particles.d 2 σdx 1 dx 2(x 1 , x 2 ) (168)• start with computing H µ µ(q 1 , q 2 , k) as a function of q 1 q 2 , q 1 k and q 2 k• since (152), you may use ∑ ɛ ɛ µɛ ∗ ν = −g µν• use the contraction identities (132) before calculating the traces!34