Precise predictions for photon pair production matched to parton showers in GENEVA

We present a new calculation for the production of isolated photon pairs at the LHC with NNLLT0 '+NNLO accuracy. This is the first implementation within the Geneva Monte Carlo framework of a process with a nontrivial Born-level definition which suffers from QED singularities. Throughout the computation we use a smooth-cone isolation algorithm to remove such divergences. The higher-order resummation of the 0-jettiness resolution variable T0 is based on a factorisation formula derived within Soft-Collinear Effective Theory which predicts all of the singular, virtual and real NNLO corrections. Starting from this precise parton-level prediction and by employing the Geneva method, we provide fully showered and hadronised events using Pythia8, while retaining the NNLO QCD accuracy for observables which are inclusive over the additional radiation. We compare our final predictions to LHC data at 7 TeV and find good agreement.

Automated summary

In this study, a new calculation method for the production of isolated photon pairs at the LHC with NNLLT0' +NNLO accuracy is presented. By implementing a process with a nontrivial Born-level definition suffering from QED singularities within the Geneva Monte Carlo framework, the researchers successfully used a smooth-cone isolation algorithm to remove divergences. The higher-order resummation of the 0-jettiness resolution variable T0, based on a factorization formula derived within Soft-Collinear Effective Theory, predicted all of the singular, virtual, and real NNLO corrections.