Subleading power corrections for N -jettiness subtractions
Here, the N -jettiness observable T N provides a way of describing the leading singular behavior of the N -jet cross section in the τ = T N = Q → 0 limit, where Q is a hard interaction scale. We consider subleading power corrections in the τ << 1 expansion, and employ soft-collinear effective theory to obtain analytic results for the dominant α s τlnτ and α 2 s τln 3 τ subleading terms for thrust in e + e – collisions and 0-jettiness for q¯q-initiated Drell-Yan–like processes at hadron colliders. These results can be used to significantly improve the numerical accuracy and stability of the N -jettiness subtraction technique for performing fixed order calculations at next-to-leading order and next-to-next-to-leading order. They reduce the size of missing power corrections in the subtractions by an order of magnitude. We also point out that the precise definition of N -jettiness has an important impact on the size of the power corrections and thus the numerical accuracy of the subtractions. The sometimes employed definition of N -jettiness in the hadronic center-ofmass frame suffers from power corrections that grow exponentially with rapidity, causing the power expansion to deteriorate away from central rapidity. This degradation does not occur for the original N -jettiness definition, which explicitly accounts for the boost of the Born process relative to the frame of the hadronic collision, and has a well-behaved power expansion throughout the entire phase space. Integrated over rapidity, using this N -jettiness definition in the subtractions yields another order of magnitude improvement compared to employing the hadronic-frame definition.