New descriptions of boson plus multiple jet production at the Large Hadron Collider in the high energy limit

Abstract

The abundance of data collected by the Large Hadron Collider (LHC) and its increasing precision and centre-of-mass energy √ s have posed challenges to the theory community. In particular, such energy increase has been shown to damage the convergence of the perturbative series of the scattering matrix S, by means of appearance of large logarithms of the form log(s/|t|) in all orders of the strong coupling gs. In future years, this effect will worsen with the advent of the Future Circular Collider (FCC), where the centre-of-mass energy is meant to be significantly larger than that of the LHC. Thus, in the high-energy limit regime, defined by s/|t| ≫ 1, the ratio of the centre-of-mass energy and the t−channel momentum exchanged squared is large, and specific formalisms have to be invoked to make accurate predictions.

In this thesis, we explore several processes for which these high-energy logarithms are numerically significant and worth taking care of appropriately. First, the origin of these logarithms will be explained and the HEJ formalism will be introduced. Next, some results for processes with a Higgs boson plus jets will be presented with comparisons to data from the LHC, before looking at the specifics of the processes involving vector boson production alongside jets. It becomes clear that for the sake of accuracy, obtaining Next-to-Leading Logarithmic expressions is important to improve the description of data in key regions, so some of the key steps towards reaching this accuracy will be analysed. Finally, it will be shown that the formalism extends to processes outside of the scope of proton-proton collision, such as Deep Inelastic Scattering, which gives a different viewpoint for tackling tensions between theory and data in the high-energy limit.