W-like measurement of the Z boson mass using dimuon events collected in pp collisions at $\sqrt{s} = 7~\mathrm{TeV}$

The mass of the Z boson is measured using a sample of $\mathrm{Z}\rightarrow\mu\mu$ events, where one of the two muons is removed from the event to form the $\mathrm{W}^\mathrm{like}$ candidate. This procedure provides a proof of principle and a quantitative validation of analysis techniques developed for a high-precision measurement of the W boson mass in $\mathrm{W}\rightarrow\mu\nu$ events. The study is made on the basis of a dimuon data sample collected by CMS at $\sqrt{s} = 7~\mathrm{TeV}$, corresponding to an integrated luminosity of $4.7~\mathrm{fb}^{-1}$. A set of $2\times10^5$ $\mathrm{Z} \rightarrow \mu \mu$ candidates is used to extract the result. The Z mass is extracted through the $\mathrm{W}^\mathrm{like}$ lepton $p_\mathrm{T}$, transverse mass and transverse missing energy distributions, and is compatible with the world-average value, $M_\mathrm{Z}^\mathrm{PDG} = 91187.6 \pm 2.1~\mathrm{MeV}$. The lowest uncertainty is obtained when using the $\mathrm{W}^\mathrm{like+}$ transverse mass, for which $M_\mathrm{Z}^\mathrm{W_{like}} = 91206 \pm 36~(\mathrm{stat.}) \pm 30~(\mathrm{syst.})~\mathrm{MeV}$.