A summary of the methods used to make a precision measurement of the Higgs boson mass is presented. The final mass value for the Higgs boson is measured to be $m_{ \rm H} = 125.26 \pm 0.21\ \mathrm{ GeV}$. This analysis considers the $\mathrm{ H} \rightarrow \mathrm{ Z}\mathrm{ Z} \rightarrow 4\ell$ channel ($\ell = e, \mu$), using proton-proton collision data collected in 2016 corresponding to an integrated luminosity of $35.9\ \mathrm{ fb}^{ -1}$ at $\sqrt{ s} = 13$ TeV by the CMS experiment at the LHC. A mass constraint is imposed on the invariant mass of the two leptons coming from the mostly on-shell Z boson to refit the lepton momenta and, hence, improve the measurement of the Higgs boson mass, per-event. The mass of the Higgs boson is extracted using a three-dimensional likelihood fit, which uses three observables per-event: (1) the refitted four-lepton invariant mass ($m'_{ 4\ell}$), (2) the refitted four-lepton mass uncertainty (${ \mathcal D}'_{ \rm mass}$), and (3) a matrix element-based kinematic discriminant (${ \mathcal D}^{ \rm kin}_{ \rm bkg}$).
Categories: hep-ex