I present the measurement of the mass of the W Boson in the electron channel using 4.4 fb.

This study examines the associated production of jets with a W boson, identified by the decay W & rarr; enu. The measurement uses the full data sample collected by the ATLAS experiment during the inaugural year of proton-proton collisions with center-of-mass energy s = 7 TeV at the Large Hadron Collider. Cross sections are presented for W & rarr; enu events with each jet multiplicity from zero through four or more jets and as a function of jet transverse momenta, the scalar sum of jet and lepton transverse momenta, the invariant mass of jets, and angular distributions. The results represent the first experimental test of perturbative QCD predictions with next-to-leading order precision for W + 4 jets.