QCD challenges in precision physics at the LHC

ongoing

In the next decade, the experiments at CERN's Large Hadron Collider (LHC) will provide us with measurements of astounding precision, by shrinking experimental uncertainties to the level of 1%. These will be crucial to probe the fundamental laws of Nature at high energies. Indeed, small deviations between measurements and predictions of the Standard Model would signal the presence of new physics. To exploit the potential of the LHC, it is imperative that theoretical predictions will match 1% accuracy. In this context, Quantum Chromodynamics (QCD) poses one of the major challanges. Due to the relatively large QCD coupling constant, perturbation theory must be pushed to the frontier of third-order corrections, or Next-to-Next-to-Next-to Leading Order (N3LO). In addition, due to the multi-scale nature of QCD processes, perturbative corrections are enhanced by large logarithms of the scale ratios, which require to resum the perturbative series. This project will provide new methodologies for QCD calculations at high precision and state-of-the-art results for two complementary classes of enhanced contributions. One are the collinear logarithms, which govern the scale dependence of the parton distribution functions (PDFs). Building upon a breakthrough discovery that I achieved in multiloop renormalisation, I will compute the N3LO evolution of the PDFs, which addresses one of the largest sources of theoretical uncertainties at the LHC and enables QCD phenomenology to reach 1% accuracy. Another class of enhancements, known as high-energy logarithms, arises when the centre-of-mass energy of the collision is much larger than the momentum transfer scale. I will tackle the factorisation of the Next-to-Next-to-Leading Logarithms (NNLLs) in multi-leg amplitudes, building on recent progress in the calculation of multi-leg amplitudes and on a new approach that I developed to disentangle the building blocks of high-energy factorisation.