Abstract
A first measurement of the W-boson mass at the LHC is presented
based on about 4.6 fb-1 of proton–proton collision data recorded in 2011 at
a centre-of-mass energy of 7 TeV with the ATLAS detector. The measured
value is 80370±19 MeV, consistent with the Standard Model prediction, with
the combined values measured at the LEP and TeVatron colliders, and with the
world average. The ATLAS result equals in precision the previous best
measurement of the W mass, performed by the CDF collaboration. During the
seminar, an overview of the analysis is given with a special emphasis on the
evaluation of the experimental systematic uncertainties, as well as on the
uncertainties due to the modelling of the vector boson production and decay.