  Low-energy strong interactions are a major source of background at hadron
colliders, and methods of subtracting the associated energy flow are well
established in the field. Traditional approaches treat the contamination as
diffuse, and estimate background energy levels either by averaging over large
data sets or by restricting to given kinematic regions inside individual
collision events. On the other hand, more recent techniques take into account
the discrete nature of background, most notably by exploiting the presence of
substructure inside hard jets, i.e. inside collections of particles originating
from scattered hard quarks and gluons. However, none of the existing methods
subtract background at the level of individual particles inside events. We
illustrate the use of an algorithm that can enable particle-by-particle
background discrimination at the Large Hadron Collider, and we envisage this as
the basis for a novel event filtering procedure upstream of the official jet
reconstruction pipelines. Our hope is that this new technique will improve
physics analysis when used in combination with state-of-the-art algorithms in
high-luminosity hadron collider environments.
