Finally we get the unpolarized cross section d σ σ d Ω Ω = 1 64 π π 2 E C M 2 | p → → f | | p → → i | | M | 2 ¯ ¯ = α α 2 2 E C M 2 { 1 t 2 ( s 2 + u 2 − − 8 m 2 ( s + u ) + 24 m 4 ) + 1 u 2 ( s 2 + t 2 − − 8 m 2 ( s + t ) + 24 m 4 ) + 2 t u ( s 2 − − 8 m 2 s + 12 m 4 ) } = α α 2 E C M 2 p 4 sin 4 ⁡ ⁡ θ θ [ 4 ( m 2 + 2 p 2 ) 2 + ( 4 p 4 − − 3 ( m 2 + 2 p 2 ) 2 ) sin 2 ⁡ ⁡ θ θ + p 4 sin 4 ⁡ ⁡ θ θ ] .