May 26 – 30, 2008
Biblioteca Universitaria, Pavia, Italy
Europe/Rome timezone

Overview on ATLAS Hadronic Calibration

May 29, 2008, 4:35 PM
Salone Teresiano (Biblioteca Universitaria, Pavia, Italy)

Salone Teresiano

Biblioteca Universitaria, Pavia, Italy

Strada Nuova, 65
oral presentation Simulation Simulation


Guennadi Pospelov (Max-Planck-Institut fuer Physik)


The jet energy scale is one of the main systematic uncertainties
in many physics
studies foreseen with the ATLAS detector. Top mass reconstruction
or measurements of
inclusive jet cross-section might be just one example relevant
for the first data taking phase already. The initial parton
energy differs from
the energy of the hadronic shower because of detector effects,
like non-compensation
and energy losses in dead material, jet algorithms and effects
from the collision physics environment.

We present the concept of the local hadronic calibration for the
ATLAS calorimeter
system as a tool to get calibrated jets at particle level for any
jet algorithm. The
procedure is based on detailed Geant 4 simulations providing
information on energy
deposits in all parts of the ATLAS detector.
In the first step topological clusters are reconstructed and
calibrated at the
electromagnetic scale. Clusters which are identified as being
are kept at the electromagnetic scale. In the next step the
energy density in
individual read-out cells is used to tag the electromagnetic
fraction in
clusters classified as hadronic and to correct for the invisible
deposits of hadrons. The energy loss in inactive material is
derived for a
given cluster from related cluster quantities. Finally out-of-cluster
corrections and out-of-jet corrections are applied to get the
final jet energy

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