A Computational Framework for Beyond-NLL Resummation of Jet Observables at Colliders

The BRUTUS (Beyond-NLL ResUmmation in a Theoretical Utility Software) project aims to develop a new theoretical framework within Quantum Chromodynamics (QCD) and Resummed Perturbation Theory. This framework will advance our understanding of particle collider physics, particularly in analysing experiments at the Large Hadron Collider (LHC).QCD calculations are crucial to LHC results, such as the Higgs boson discovery in 2012. At LHC energies, a perturbative description of strong interactions is valid, and jet observables— like event and jet shapes—are essential for testing QCD. While Fixed Order calculations are accurate for hard radiation, resummed calculations are necessary in regions dominated by multiple soft-collinear emissions. Here, the perturbative expansion struggles due to large logarithms, requiring a systematic approach. Next-to-leading logarithmic (NLL) resummations are available for many observables through the program CAESAR, but next-to-next-to-leading logarithmic (NNLL) resummations, although developed for specific cases, lack a public, automated framework.This project aims to revolutionize the CAESAR framework, developing the BRUTUS computer program, to fulfil this requirement. BRUTUS will extend prediction to higher accuracy and to non-global jet observables, not described by CAESAR. The recent influx of high-quality data from LHC Run 3 and the upcoming High-Luminosity LHC (HL-LHC) program underscores the need for more accurate theoretical predictions, which will be obtained in a flexible and lightweight way with BRUTUS.