Performance of the missing transverse energy reconstruction in first ATLAS data at a center-of-mass energy of 7 TeV

The performance of the missing transverse energy (Etmiss) reconstructed with the ATLAS detector is assessed using a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV collected in April and May 2010. We report on results in randomly-triggered events, soft proton proton collisions and collisions with jets at high transverse momentum. Particular attention is given to tails in the Etmiss distribution and to the measurement of the Etmiss resolution.