VALIDATION OF THE HADRONIC CALIBRATION OF THE ATLAS CALORIMETER WITH TESTBEAM DATA CORRESPONDING TO THE PSEUDORAPIDITY RANGE $2.5<|eta|<4.0$}

The pseudorapidity region $2.5<|eta|<4.0$ in ATLAS is a particularly complex transition zone between the endcap and forward calorimeters. A set-up consisting of 1/4 resp. 1/8 of the full azimuthal acceptance of the ATLAS liquid argon endcap and forward calorimeters has been exposed to beams of electrons, pions and muons in the energy range $E < 200 GeV$ at the CERN SPS. Data have been taken in the endcap and forward calorimeter regions as well as in the transition region. This beam test set-up corresponds very closely to the geometry and support structures in ATLAS. Pion data have been analyzed using the standard local hadronic calibration scheme as forseen for the ATLAS calorimeter. In particular the weighting scheme to compensate for the different electron to pion response as well as corrections for dead material in the transition region have been extensively tested and compared to simulation based on GEANT 4 models.