Drift Time measurement in the ATLAS Liquid Argon electromagnetic calorimeter using cosmic muons

In this article, measurements of the drift time (Tdrift) of the ionization electrons in the ATLAS ElectroMagnetic (EM) calorimeter are presented, using 32-samples cosmic muon data. In particular, the drift time measurement is used to assess the intrinsic uniformity of the calorimeter gaps and estimate its impact on the constant term of the energy resolution. This analysis leads to an estimated contribution to the constant term of (0.29+0.05-0.04) % in the barrel and (0.54+0.06-0.04) % in the endcaps. The same data are used to measure the drift velocity of ionization electrons in liquid argon, which is found to be 4.61 ± 0.07 mm/μs at 88.5 K and 1 kV/mm.