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

The $W$ boson mass is one of the most interesting fundamental parameters of the Standard Model of particle physics, as it allows for model-independent probes for effects of new physics. In this work, proton-proton data recorded by the ATLAS detector in 2011, at a center of mass energy of $7~\text{TeV}$, that were used for the first $W$ boson mass measurement at the LHC, have been reanalyzed with an advanced fitting technique based on a profile likelihood approach. This allows for a reduction of several systematic uncertainties. Advances in the modelling of the parton density functions of the proton in recent years have been taken into account and a more modern PDF set has been chosen as baseline. The updated measurement yields a preliminary value of $m_W = 80360 \pm 5 (\text{stat.}) \pm 15 (\text{syst.}) = 80360 \pm 16~\text{MeV}$, where the first uncertainty component is statistical and the second corresponds to the experimental and physics-modelling systematic uncertainty. This result is compatible with the published value and its uncertainty improved by 15%.