Dr. William J. Torres Bobadilla published together with other scientists from different institutions a review in the European Journal of Physics C (EPJC). This review is an outcome of the workshop "Paving the way to alternative NNLO strategies" held in November 2019 at the Galileo Galilei Institute For Theoretical Physics in Florence.
The main idea is to establish a connection between the data delivered by the collider experiments at CERN and the various techniques that deal with predictions at Next-to-Next-to-Leading Order (NNLO). In effect, calculations at NNLO are not straightforward, which is caused by the presence of physical singularities, ultraviolet, infrared and thresholds. The review collects approaches that aim for local cancellations of these singularities. The cancellations make it possible to create more stable numerical evaluations, rendering in this way easy physical observables to compute. The singularities are locally cancelled at integrand level, allowing to perform an integration in purely four dimensions.
In the spirit of showing methods to deal with NNLO calculations, a general description together with illustrative applications is presented. On top of it, remarks on the strengths and weaknesses of the various methods are provided to show the reader what is available and what can be improved.