A measurement of the soft-drop jet mass in pp collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

TL;DR

This paper presents the first measurement at a hadron collider of a jet substructure observable calculated at next-to-next-to-leading-logarithm accuracy, comparing data with advanced QCD predictions to enhance understanding of jet properties.

Contribution

It provides the first experimental measurement of a jet substructure quantity at NNLL accuracy, bridging the gap between theoretical calculations and collider data.

Findings

Data agree with NNLL QCD calculations within uncertainties.

Leading-log Monte Carlo simulations show partial agreement.

Results improve understanding of jet substructure at high energies.

Abstract

Jet substructure observables have significantly extended the search program for physics beyond the Standard Model at the Large Hadron Collider. The state-of-the-art tools have been motivated by theoretical calculations, but there has never been a direct comparison between data and calculations of jet substructure observables that are accurate beyond leading-logarithm approximation. Such observables are significant not only for probing the collinear regime of QCD that is largely unexplored at a hadron collider, but also for improving the understanding of jet substructure properties that are used in many studies at the Large Hadron Collider. This Letter documents a measurement of the first jet substructure quantity at a hadron collider to be calculated at next-to-next-to-leading-logarithm accuracy. The normalized, differential cross-section is measured as a function of log$_{10}\rho^2$, where $\rho$ is the ratio of the soft-drop mass to the ungroomed jet transverse momentum. This quantity is measured in dijet events from 32.9 fb$^{-1}$ of $\sqrt{s} = 13$ TeV proton-proton collisions recorded by the ATLAS detector. The data are unfolded to correct for detector effects and compared to precise QCD calculations and leading-logarithm particle-level Monte Carlo simulations.