Speaker
Description
Calculations in perturbative QCD suffer from large logarithms that appear at all orders in perturbation theory, endangering the perturbative description. In pursuit of precise predictions for cross sections, factorisation theorems have been established with the benefit to resum these large logarithms to all orders in perturbation theory, improving the predictive power of the theory. This procedure is well understood at leading power (LP) in these large logarithms, but much work is still to be done at next-to-leading power (NLP). In order to better understand the NLP structure, a factorisation theorem has been developed at this accuracy within diagrammatic QCD. This introduces new jet functions that contribute to this subleading power behaviour. We verify the factorisation theorem by giving definitions to these new jet functions and calculate them up to two loops. We compare their contributions to a region calculation of the two-loop massive fermion form factor and find perfect agreement.
