Evidence for vector boson scattering in events with four leptons and two jets in proton-proton collisions at sqrt(s) = 13 TeV

A search for the electroweak production of two Z bosons in association with two jets and constraints on anomalous quartic gauge couplings are presented. The analysis is based on a data sample of proton-proton collisions at $\sqrt{s}=13~\textrm{TeV}$ collected with the CMS detector in 2016, 2017 and 2018, and corresponding to an integrated luminosity of $137.1~\mathrm{fb}^{-1}$. The search is performed in the fully leptonic final state $ZZ\to\ell\ell\ell'\ell'$, where $\ell,\ell' = e, \mu$. The electroweak production of two jets in association with two Z bosons is measured with an observed (expected) significance of 4.0 (3.5) standard deviations. Fiducial cross sections for the electroweak production are measured and the fiducial cross section is $\sigma_{\mathrm{EW}}(pp\rightarrow ZZjj\rightarrow\ell\ell\ell'\ell'jj)$ = 0.33 $^{+0.11}_{-0.10}\,{\mathrm{(stat)}}\,^{+0.04}_{-0.03}\,\mathrm{(syst)}$ fb in the most inclusive volume, in agreement with the standard model prediction. Limits on anomalous quartic gauge couplings are derived in terms of the effective field theory operators T0-2 and T8-9.