B2a Automated Calculations in Soft-Collinear Effective Theory

Soft-Collinear Effective Theory (SCET) is an efficient tool to perform resummations for collider observables. Starting from a factorisation theorem that separates the effects from hard, collinear and soft QCD radiation, logarithmic corrections to e+e− event-shape variables (Fig. 1) or hadron-collider distributions (Fig. 2) can be resummed using renormalisation group techniques. The goal of this project consists in optimising the existing SCET technology to improve the theoretical predictions for a large class of LHC observables. To this end, the computation of two-loop soft, jet and beam functions will be automated and the first automated resummation code in SCET will be developed. As the soft and collinear functions constitute the required counterterms for fixed-order QCD computations, the project also paves the way for novel NNLO calculations for processes with higher jet multiplicities and top-quark observables

1. Soft functions
   • Extension of SoftSERVE to processes with aribtrary number of jets
   • Development of a similar code for top-quark related soft functions
2. Development of an automated resummation code for e+e− observables ◦ Comparison to the CAESAR/ARES approach
   • Extension to hadron-collider observables
3. SCET subtractions
   • $N$ -jettiness subtraction for processes with more than one jet
   • $q_\perp$ subtraction for (associated) tt ̄ production
   • Studies to improve performance of NNLO subtraction/slicing techniques