Combination of ATLAS and CMS results on the mass of the top-quark using up to 4.9 fb$^{-1}$ of $\sqrt{s}=7$ TeV LHC data

A combination of top-quark mass measurements performed\n by the ATLAS and CMS experiments at the LHC is presented. The\n dataset used corresponds to an integrated luminosity per experiment of\n up to 4.9 $\rm fb^{-1}$ of proton-proton collisions at a\n centre-of-mass energy of 7 TeV. The combination includes\n measurements in the $t\bar t\to \rm lepton+jets$, $t\bar t \to \rm di-lepton$ and $t\bar t\to \rm all-jets$ channels. The resulting\n preliminary combined LHC measurement of the top-quark mass is\n $m_{\rm top} = 173.29 \pm 0.23 \mbox{ (stat)} \pm 0.92 \mbox{ (syst)}$\n GeV, with a total uncertainty of $0.95$ GeV.