Performance of the combined ATLAS Liquid Argon End-Cap Calorimeters in Beam Tests at the CERN SPS

In 2002 for the first time modules of the ATLAS liquid argon Electromagnetic and Hadronic End-cap Calorimeters (EMEC and HEC) were combined and exposed to beams of electrons, pions and muons in the energy range $6 GeV \leq E \leq 200 GeV$ at the CERN SPS. The entire calibration chain is studied from the discrete measured samples of the ionization signals in the EMEC and HEC to the reconstructed energies for electrons, pions and muons. This includes the reconstruction of the ionization signal with the optimal filter technique and the event by event combination of the read-out cells to clusters using a topological neighboring criterion. The calibration constant between the total ionization signal and the deposited energy for electrons in the EMEC is determined to be $\alpha_{EMEC}^{EM}=(0.3855 \pm 0.0004 )\frac {MeV} {nA}$ (statistical error only) and the linearity of the response to electrons is observed to be within $\pm$0.5\%. The typical intrinsic energy resolution for electrons is found to be $\frac{\sigma'(E)}{E}=\frac{(12.1 \pm 0.2)\%}{\sqrt{E/GeV}} \oplus (0.4 \pm 0.1)\%$, which does not include typical electronics noise values between 200 and 300 MeV. For the energy reconstruction of pions two signal weighting approaches are developed. The intrinsic energy resolution for negative pions is measured to be typically $\frac{\sigma'(E)}{E}=\frac{(80.7 \pm 0.4)\%}{\sqrt{E/GeV}} \oplus (0 \pm 0.3)\%$, not including the electronics noise of 1.0 up to 1.6 GeV. Muon signals are reconstructed with a mean signal to noise ratio of $4.87 \pm 0.10$ and $4.18 \pm 0.07$ in the EMEC and in the HEC, respectively. The relative response of the EMEC and HEC to electrons normalized to the response to muons is determined to be $\left(e/\mu\right)_{EMEC}= 0.803 \pm 0.003 \pm 0.012$ and $\left(e/\mu\right)_{HEC1}= 0.98 \pm 0.01 \pm 0.04$ (statistical and systematic errors, respectively). All results are compared to detailed Monte Carlo simulations.