Two-loop splitting functions in QCD

We present the universal two-loop splitting functions that describe the limits of two-loop n-point amplitudes of massless particles when two of the momenta are collinear. To derive the splitting amplitudes, we take the collinear limits of explicit two-loop four-point helicity amplitudes computed in the 't Hooft-Veltman scheme. The g → gg splitting amplitude has recently been computed using the unitarity sewing method and we find complete agreement with the results of ref. The two-loop q → qg and g → qq̄ splitting functions are new results. We also provide an expression for the two-loop soft splitting function. © SISSA/ISAS 2004.