UC Irvine

A measurement of the mass of the W boson is presented based on proton–proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6fb-1$$4.6~\hbox {fb}^{-1}$$ of integrated luminosity. The selected data sample consists of 7.8×106$$7.8\times 10^6$$ candidates in the W→μν$$W\rightarrow \mu u $$ channel and 5.9×106$$5.9\times 10^6$$ candidates in the W→eν$$W\rightarrow e u $$ channel. The W-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the W boson transverse mass in the electron and muon decay channels, yielding mW=80370±7(stat.)±11(exp. syst.)±14(mod. syst.)MeV=80370±19MeV,$$\begin{aligned} onumber m_W = 80370&\pm 7~(\text {stat.}) \pm 11 (\text {exp. syst.}) \&\pm 14~(\text {mod. syst.})~\text {MeV} \ = 80370&\pm 19\,\text {MeV}, \end{aligned}$$where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the W+$$W^+$$ and W-$$W^-$$ bosons yields mW+-mW-=-29±28$$m_{W^+}-m_{W^-} = -\,29 \pm 28$$ MeV.