Evidence for electroweak production of four charged leptons and two jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports the first evidence for electroweak production of two Z bosons with two jets at 13 TeV, measuring cross sections and setting limits on anomalous gauge couplings using CMS data.

Contribution

It provides the first evidence for electroweak ZZjj production at 13 TeV and measures its cross section, also constraining anomalous quartic gauge couplings.

Findings

Observed significance of 4.0 standard deviations.

Measured cross section of 0.33 fb in the most inclusive volume.

Set limits on anomalous quartic gauge couplings.

Abstract

Evidence is presented for the electroweak (EW) production of two jets (jj) in association with two Z bosons and constraints on anomalous quartic gauge couplings are set. The analysis is based on a data sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV collected with the CMS detector in 2016-2018, and corresponding to an integrated luminosity of 137 fb$^{-1}$. The search is performed in the fully leptonic final state ZZ $\to$ $\ell\ell\ell'\ell'$, where $\ell,\ell' = $ e, $\mu$. The EW production of two jets in association with two Z bosons is measured with an observed (expected) significance of 4.0 (3.5) standard deviations. The cross sections for the EW production are measured in three fiducial volumes and the result is $\sigma_{\mathrm{EW}}$(pp $\to$ ZZjj $\to$ $\ell\ell\ell'\ell'$jj) = 0.33 $^{+0.11}_{-0.10}$ (stat) $^{+0.04}_{-0.03}$ (syst) fb in the most inclusive volume, in agreement with the standard model prediction of 0.275 $\pm$ 0.021 fb. Measurements of total cross sections for jj production in association with two Z bosons are also reported. Limits on anomalous quartic gauge couplings are derived in terms of the effective field theory operators T0, T1, T2, T8, and T9.