Underlying Event properties in pp collisions at $\sqrt{s}$ = 13 TeV
JHEP 2004 (2020) 192, 2020.
The collaboration

Abstract (data abstract)
This article reports measurements characterizing the Underlying Event (UE) associated with hard scatterings at mid-rapidity ($|\\eta| <$ 0.8) in pp collisions at $\\sqrt{s} =$ 13 TeV. The hard scatterings are identified by the leading particle, the charged particle with the highest transverse momentum ($p_{T}^{leading}$) in the event. Charged-particle numbers and summed transverse-momentum densities are measured in different azimuthal regions defined with respect to the leading particle direction: Toward, Transverse, and Away. The Toward and Away regions contain the fragmentation products of the hard scatterings in addition to the UE contribution, whereas particles in the Transverse region are expected to originate predominantly from the UE. The study is performed as a function of $p_{T}^{leading}$ with three different $p_{T}$ thresholds for the associated particles, $p_{T}^{track} >$ 0.15, 0.5, and 1.0 GeV/$c$.