QED at NNLO with McMule

Abstract

McMule is a framework for fully differential higher-order QED calculations of scattering and decay processes involving leptons. It keeps finite lepton masses, which regularises collinear singularities. Soft singularities are treated with dimensional regularisation and using FKS^\ellℓ subtraction. We describe the implementation of the framework in Fortran 95, list the processes that are currently implemented, and give instructions on how to run the code. In addition, we present new phenomenological results for muon-electron scattering and lepton-proton scattering, including the dominant NNLO corrections. While the applications presented focus on MUonE, MUSE, and P2, the code can be used for a large number of planned and running experiments.

NNLO virtual and real leptonic corrections to muon-electron scattering

“…[47] and supplemented with a subtraction scheme for QED calculations with massive fermions at NNLO accuracy [48]. More recently, the exact NNLO photonic corrections along the electron line, including all finite mass terms, have been implemented in two independent MC tools, Mesmer [49] and McMule [50]. In the former, the framework for the complete photonic NNLO calculation has been built and made available, including the full NLO calculation to the process µe → µeγ and the LO double radiative process µe → µeγγ.…”

Status of the MUonE experiment

“…For a state-of-the-art review see [18] and references therein. On top of that a further milestone was recently achieved by the development of two independent fully exclusive MC codes, featuring the exact NNLO photonic corrections on the leptonic legs, including all mass terms [19,20]. Their results have been compared and are in very good agreement.…”

Towards muon-electron scattering at NNLO

“…Thanks to this common effort, we agreed with the authors of ref. [39] to proceed in parallel and make our results public at the same time.…”