  The reconstruction of the signal from hadrons and jets emerging from the
proton-proton collisions at the Large Hadron Collider (LHC) and entering the
ATLAS calorimeters is based on a three-dimensional topological clustering of
individual calorimeter cell signals. The cluster formation follows cell
signal-significance patterns generated by electromagnetic and hadronic showers.
In this, the clustering algorithm implicitly performs a topological noise
suppression by removing cells with insignificant signals which are not in close
proximity to cells with significant signals. The resulting topological cell
clusters have shape and location information, which is exploited to apply a
local energy calibration and corrections depending on the nature of the
cluster. Topological cell clustering is established as a well-performing
calorimeter signal definition for jet and missing transverse momentum
reconstruction in ATLAS.
