The goal of the internship will be to understand techniques and concepts of Next-To-Leading Order (NLO) calculations, which involves computing both virtual 1-loop and real radiation diagrams. Individual contributions will exhibit different type of singularities in the dimensional regulator. The student will learn these concepts and also aspects related to renormalisation and factorisation in the framework of quarkonium production. Charmonium and bottomonium production, bound states consisting of a heavy quark and its anti-quark, cc and bb pairs respectively, provide interesting opportunities to study the interplay between the perturbative and non-perturbative regimes of Quantum Chromodynamics (QCD) which is at the heart of formation of hadrons such as the proton. See for more details the description in the PDF file and references therein.