sigma (E_{1},E_{2}) = (2pi)^4int frac{d^{3}mathbf p_{3}}{(2pi)2E_{3}}frac{d^{3}mathbf p_{4}}{(2pi)^{3}2E_{4}}frac{d^{3}mathbf p_{5}}{(2pi)^{3}2E_{5}}|M(mathbf p_{1}, mathbf p_2, mathbf p_3,mathbf p_4,mathbf p_5)|^2frac{delta^{4}(p_1+p_2-p_3-p_4-p_5)}{v_{text{relative}}}