Improved $W$ boson Mass Measurement using 7 TeV Proton-Proton Collisions with the ATLAS detector

In 2017, the ATLAS collaboration measured the $W$ boson mass using pp- collision data taken at $\sqrt{s}=7\;$TeV in 2011, resulting in a precision of 19 MeV. We present a revised analysis of the same dataset, improving the fit methods and including a measurement of the width of the $W$ boson. A precise measurement of these quantities in the decay of the $W$ boson represent an excellent precision test of the Standard Model (SM). A detailed comparison with the previous analysis design will be presented. In particular, the estimate of the multi-jet background and the treatment of some systematic uncertainties have been improved. In addition, a newly developed profile likelihood fit is used to improve the statistical interpretation of the measurement. The carefully performed cross-checks with the previous results will be discussed.