Observation of the $Z\rightarrow 4\ell$ decay and use of $Z\rightarrow 4\ell$ for calibrations of the measured cross section and scale of the new boson near 125 GeV in the $H\rightarrow ZZ\rightarrow 4\ell$ channel

$Z\rightarrow 4\ell$ decays were first observed in pp collisions at the CMS detector in 2011. These decays are especially useful as a standard candle for the new boson near 125 GeV in the $H\rightarrow ZZ\rightarrow 4\ell$ channel due to their kinematic similarity and proximity in mass. The $Z\rightarrow 4\ell$ peak has a well measured mass and therefore can be used to calibrate the scale of the new boson. Here an update on the observation of the $Z\rightarrow 4\ell$ decays is presented, as well as results using the $Z\rightarrow 4\ell$ peak as a calibration tool for the new boson near 125 GeV.