Measurement of the W-boson mass at the ATLAS experiment

We present the results of $W$-boson mass measurements with the ATLAS detector at the LHC based on the 2011 data-set recorded at a centre-of-mass energy of $\sqrt{s} =7$~\TeV, and corresponding to 4.6~fb$^{-1}$ of integrated luminosity. The selected data sample consists of 7.8$\times 10^6$ $W\rightarrow \mu\nu$ candidates and 5.9$\times 10^6$ $W\rightarrow e\nu$ candidates. Measurements are performed through template fits to transverse momentum distributions of charged leptons as well as to transverse mass distributions of the $W$-boson in electron and muon decay modes in various kinematic categories. All the individual measurements are found to be consistent and their combination leads to a value of \begin{eqnarray} \nonumber m_W &=& 80371.1 \pm 6.7~\text{MeV} (\textrm{stat.}) \pm 10.7~\text{MeV} (\textrm{exp.sys.}) \pm 13.6~\text{MeV} (\textrm{mod.sys.}) \\ \nonumber &=& 80371.1 \pm 18.6~\text{MeV}, \end{eqnarray} The measured value of the $W$-boson mass is compatible with the current world average of $m_W = 80385 \pm 15~\text{MeV}$. The uncertainty is competitive with the current most precise measurements performed by the CDF and D0 collaborations.