Abstract (data abstract)

This paper presents a measurement of the electroweak production of two jets in association with a $Z\gamma$ pair, with the $Z$ boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector and corresponding to an integrated luminosity of 139 fb$^{-1}$. The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak $Z\gamma$ production in association with two jets is obseved in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31 $\pm$ 0.29 fb. An observed (expected) upper limit of 0.37 (0.34) at 95% confidence level is set on the branching ratio of a 125 GeV Higgs boson to invisible particles, assuming the Standard Model production cross-section. The signature is also interpreted in the context of decays of a Higgs boson into a photon and a dark photon. An observed (expected) 95% CL upper limit on the branching ratio for this decay is set at 0.018 (0.017), assuming the Standard Model production cross-section for a 125 GeV Higgs boson.

Figure 3

Data from figure 3

10.17182/hepdata.107760.v1/t1

Post-fit results for all $m_\text{jj}$ SR and CR bins in the EW $Z \gamma + \text{jets}$ cross-section measurement with the...
Figure 4

Data from figure 4

10.17182/hepdata.107760.v1/t2

Post-fit results for all DNN SR and CR bins in the search for $H \to \text{inv.}$ with the $\mathcal{B}_\text{inv}$ signal...
Figure 5

Data from figure 5

10.17182/hepdata.107760.v1/t3

Post-fit results for the ten [$m_\text{jj}$, $m_\text{T}$] bins constituting the SR and CRs defined for the dark photon search with...
Figure 6

Data from figure 6

10.17182/hepdata.107760.v1/t4

Post-fit $m_\text{T}(\gamma, E_\text{T}^\text{miss})$ distribution in the inclusive signal region for the dark-photon search with the 125 GeV mass $\mathcal{B}(H \to...
Figure 7

Data from figure 7

10.17182/hepdata.107760.v1/t5

The 95% CL upper limit on the Higgs boson production cross-section times branching ratio to $\gamma \gamma_\text{d}$ is shown for...
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Data from figure 1 of auxiliary material

10.17182/hepdata.107760.v1/t6

Post-fit $m_\text{jj}$ distribution in the inclusive signal region. The Higgs boson invisible decay signal is scaled to a $\mathcal{B}_\text{inv}$ of...
Auxiliary figure 2

Data from figure 2 of auxiliary material

10.17182/hepdata.107760.v1/t7

Post-fit $m_\text{jj}$ distribution in the one-lepton control region $W_{\ell \nu}^\gamma$ CR. Events with $m_\text{jj}$ larger than the rightmost bin boundary...
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Data from figure 3 of auxiliary material

10.17182/hepdata.107760.v1/t8

Post-fit $m_\text{T}$ distribution in the one lepton control region. Events with $m_\text{T}$ larger than the rightmost bin boundary are added...
Auxiliary figure 4

Data from figure 4 of auxiliary material

10.17182/hepdata.107760.v1/t9

Post-fit photon centrality distribution in the zero lepton signal plus control region with the $\mathcal{B}_\text{inv}$ signal normalization set to zero...
Auxiliary figure 5

Data from figure 5 of auxiliary material

10.17182/hepdata.107760.v1/t10

Post-fit photon $E_\text{T}$ distribution in the zero lepton signal region with the $\mathcal{B}_\text{inv}$ signal normalization set to zero in the...
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Data from figure 6 of auxiliary material

10.17182/hepdata.107760.v1/t11

Post-fit photon centrality distribution in the zero lepton signal plus control region resulting from the fit to the $m_\text{jj}$ distribution...
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Data from figure 7 of auxiliary material

10.17182/hepdata.107760.v1/t12

Post-fit photon $E_\text{T}$ distribution in the zero lepton signal region resulting from the fit to the $m_\text{jj}$ distribution for EW...
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Data from figure 8 of auxiliary material

10.17182/hepdata.107760.v1/t13

Post-fit DNN output score distribution in the one lepton control region.
Auxiliary table 1

Data from table 1 of auxiliary material

10.17182/hepdata.107760.v1/t14

Yields for the EW $Z \gamma + \text{jets}$ process are shown after each selection along with relative and absolute signal...
Auxiliary table 2

Data from table 2 of auxiliary material

10.17182/hepdata.107760.v1/t15

Yields for the 125 GeV Higgs boson with $\mathcal{B}_\text{inv.} =$ 1 signal produced by the vector boson fusion process in...
Auxiliary table 3

Data from table 3 of auxiliary material

10.17182/hepdata.107760.v1/t16

Yields for the 125 GeV Higgs boson with $\mathcal{B}(H \to \gamma \gamma_\text{d}) =$ 1 signal produced by the vector boson...

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