[@Khachatryan:2014kca]. All of these samples are generated using the generator for the description of NLO QCD effects in the production mechanism, and <span style="font-variant:small-caps;">JHUGen</span> [@Gao:2010qx; @Bolognesi:2012mm; @Anderson:2013afp] to describe the decay of these exotic resonances to four leptons including all spin correlations.

The MC event samples that are used to estimate the contribution from the background process $\Pg\Pg \to \PZ \PZ$ are simulated using <span style="font-variant:small-caps;">MCFM 6.7</span> [@Campbell:2011bn], while the background process $\PQq\PAQq \to 4\ell$ is simulated at NLO accuracy with the generator including $s$-, $t$-, and $u$-channel diagrams. For the purpose of the ${\ensuremath{\PZ \to 4\ell}\xspace}$ cross section measurements, we have also separately modelled contributions from the $t$- and $u$-channels of the $\PQq\PAQq~(\to \PZ \PZ^{*})\to 4\ell$ process at NLO accuracy with .

All the event generators described above take into account the initial- and final-state QED radiation (FSR) effects which can lead to the presence of additional hard photons in an event. Furthermore, the and <span style="font-variant:small-caps;">JHUGen</span> event generators take into account interference between all contributing diagrams in the ${\ensuremath{\PH \to 4\ell}\xspace}$ process, including those related to the permutations of identical leptons in the $4\Pe$ and $4\mu$ final states. In the case of the LO, NLO, and NNLO generators, 