We report on a major milestone in the construction of logarithmically accurate final-state parton showers, achieving next-to-next-to-leading-logarithmic (NNLL) accuracy for the wide class of observables known as event shapes. The key to this advance lies in the identification of the relation between critical NNLL analytic resummation ingredients and their parton-shower counterparts. Our analytic discussion is supplemented with numerical tests of the logarithmic accuracy of three shower variants for more than a dozen distinct event-shape observables in Z→qqˉ and Higgs →gg decays. The NNLL terms are phenomenologically sizeable, as illustrated in comparisons to data.
@article{arxiv.2406.02661,
title = {A new standard for the logarithmic accuracy of parton showers},
author = {Melissa van Beekveld and Mrinal Dasgupta and Basem Kamal El-Menoufi and Silvia Ferrario Ravasio and Keith Hamilton and Jack Helliwell and Alexander Karlberg and Pier Francesco Monni and Gavin P. Salam and Ludovic Scyboz and Alba Soto-Ontoso and Gregory Soyez},
journal= {arXiv preprint arXiv:2406.02661},
year = {2025}
}
Comments
6 pages plus supplemental material; v2: matches the version published in Phys. Rev. Lett.; public code available as part of 0.2.0 release of PanScales, https://gitlab.com/panscales/panscales-0.X