Speaker
Description
In the context of infrared subtraction algorithms beyond next-to-leading order, it
becomes necessary to consider multiple infrared limits of scattering amplitudes, in which
several particles become soft or collinear in a strongly ordered sequence. We study these
limits from the point of view of infrared factorisation, and we provide general definitions of
strongly-ordered soft and collinear kernels in terms of gauge-invariant operator matrix
elements. With these definitions in hand, it is possible to construct local subtraction
counterterms for strongly ordered congurations. These are building blocks of infrared-finite
soft and collinear cross sections, therefore, upon integration, they cancel virtual poles by
construction. We test these ideas at tree level for multiple emissions, and at one
loop for single emission, which is sufficient for NNLO subtraction.
