Collinear limits beyond the leading order from the scattering equations

Understand

The structure of tree-level scattering amplitudes for collinear massless bosons is studied beyond their leading splitting function behavior.

• These near-collinear limits at sub-leading order are best studied using the Cachazo-He-Yuan (CHY) formulation of the S-matrix based on the scattering equations.
• We compute the collinear limits for gluons, gravitons and scalars.
• It is shown that the CHY integrand for an n-particle gluon scattering amplitude in the collinear limit at sub-leading order is expressed as a convolution of an (n-1)-particle gluon integrand and a collinear kernel integrand, which is universal.