!resolution.jpg|thumbnail,align=left!Introduction

In this exercise we will use LCDD, an extension of the standard Geant4 GDML format, to describe a complete detector setup, including sensitive detectors and readout. Since we are using XML to configure Geant4 there is no need to write any C++ code.  We can use a version of SLIC which has been pre-built with support for GDML included. In this example we will use a simple test beam like calorimeter consisting of lead glass blocks of 1 cubic cm. For each calorimeter cell we read out the Ionization loss as well as the energy deposited by cherenkov photons.

Principle of a dual read out calorimeter

For e+, e- and  photons the total energy of the incoming particle is converted into detectable kinetic energy of electrons leading to excellent energy resolution for electrons/photons. Hadrons  on the other hand break nuclei and liberate nucleons/nuclear fragments. Even if the kinetic energy of the resulting nucleons is measured, the significant fraction of energy is lost to overcome the binding energy. Fluctuations of the number of broken nuclei dominate fluctuations of the observed energy leading to a relatively poor energy resolution for hadrons.