Search for new physics using boosted Z bosons decaying to electrons in proton--proton collisions at $\sqrt{s}$ = 8 TeV

A search for new heavy particles whose two-body decays involve boosted Z bosons is presented, based on the dielectron decay channel, using $19.7~\mathrm{fb}^{-1}$ of $\sqrt{s}=8~\mathrm{TeV}$ proton--proton collision data collected by the CMS detector in 2012. No evidence for non-standard-model physics is observed in the inclusive Z boson transverse momentum spectrum, and upper limits on the cross section for production of excited quarks decaying to qZ are obtained. The analysis excludes, at $95\%$ confidence level, the production of excited quarks decaying to qZ for excited quark masses below $2.6~\mathrm{TeV}$ ($3.0~\mathrm{TeV}$) in gauge (contact) interaction production modes, under the standard assumption of $f=f'=f_s=1$.