Evidence of $ZZ\gamma$ Production with the ATLAS Detector

Abstract

This Letter presents the first evidence of the simultaneous production of two $Z$ bosons and one photon with the ATLAS detector at the Large Hadron Collider. The measurement is performed using the full Run-2 dataset, recorded from 2015 to 2018, of proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 140 fb${}^{-1}$. The fully leptonic final state with four leptons and one photon is analyzed, $pp\to ZZ\gamma \to {\ell }^{+}{\ell }^{-}{\ell }^{\prime +}{\ell }^{\prime -}\gamma$ with $\ell ,{\ell }^{\prime }=e$ or $\mu$. This final state is measured in a fiducial region where photon final-state radiation is minimized, and the photon has a transverse momentum of $p_{\mathrm{T}}^{\gamma }>20$ GeV. Eight events are selected, with a background estimate of $0.92\pm 0.15$. This results in an observed (expected) significance of the $ZZ\gamma$ final state of $4.4\sigma$ ($4.0\sigma$). The measured cross-section for $pp\to ZZ\gamma \to {\ell }^{+}{\ell }^{-}{\ell }^{\prime +}{\ell }^{\prime -}\gamma$ in the fiducial region is ${\sigma }_{ZZ\gamma }=0.144_{-0.051}^{+0.065}{\text{ (stat.)}}_{-0.004}^{+0.008}\text{ (syst.) fb}$, in agreement with the Standard Model prediction of ${\sigma }_{\text{fid.}}^{\text{SM}}=0.130\pm 0.006$ fb.

Comments: 30 pages in total, author list starting page 15, 2 figures, 3 tables, published in PRL. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2023-14/

Cited by in corpus (1)

• Evidence of ZZ$\gamma$ production and observation of $4\ell \gamma$ in proton-proton collisions at $\sqrt{s}$ = 13 TeV