Refined reconstruction and calibration of the missing transverse energy in the ATLAS detector

The measurement of the missing transverse energy (\etmiss) is fundamental for many analyses at LHC. Good etmiss resolution and calibration are essential for searches of new physics as well as precise measurements. We describe a refined reconstruction and calibration of etmiss developed by ATLAS and its performances on events containing Z and W bosons. The data sample was collected in proton-proton collisions at a center-of-mass energy of 7 TeV, and corresponds to an integrated luminosity of about 36 \ipb. The determination of the absolute scale of the etmiss, fundamental for determining systematic uncertainties in all analysis involving etmiss measurements, is also presented.