Figure 01a

The diagrams showing different types of pp->chichi+Z production modes considered in this analysis. Figure (a) shows the diagram of an ISR operator, and figure (b) shows the diagram of a ZZchichi operator.

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Figure 01b

The diagrams showing different types of pp->chichi+Z production modes considered in this analysis. Figure (a) shows the diagram of an ISR operator, and figure (b) shows the diagram of a ZZchichi operator.

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Figure 02

Shape of the MET distribution in simulated samples of ZZ background, effective field theories of dark-matter interaction with a qq initial state (D1, D5, and D9 and interaction with a Z/gamma* intermediate state, and the scalar-mediator theory. The shapes of ZZchichi-no-gamma* and ZZchichi-maximal-gamma* are similar, as are the shapes of D9 and the dimension-5 ZZchichi EFT, so only one of each is plotted. Each distribution is normalized to unit area. The mass of the scalar mediator, $m_{eta}$ is 1 TeV, and the dark-matter particle mass is m_{chi}=200 GeV.

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Figure 03

MET distributions after all event selections other than the MET thresholds for the observed data; the expected SM backgrounds taken from simulation; the hypothetical pp->Zchichi signals for different values of the mass scale, M_{star}. The dark-matter particle mass is m_{chi}=200 GeV. The last bin contains the events with MET>450 GeV. The ratio of data to simulated backgrounds is also shown. The band shows the experimental systematic uncertainties on the ratio.

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Figure 04

Observed 90% C.L. lower limits on the mass scale, M_star, of considered effective field theories as a function of m_chi. For each operator, the values below the corresponding line are excluded.

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Figure 05

Observed 90% C.L. upper limits on the chi-nucleon scattering cross section as a function of m_{chi} for the spin-dependent D9 effective operators mediating the interaction of the dark-matter particles with the qq initial state. The limits are compared with results from the published ATLAS hadronically decaying W/Z and j+chichi searches, COUPP, SIMPLE, PICASSO, and IceCube. These limits are shown as they are given in the corresponding publications and are only shown for comparison with our results, since they are obtained assuming the interactions are mediated by operators different from those used for the ATLAS limits.

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Figure 06

Observed 90% C.L. upper limits on the chi-nucleon scattering cross section as a function of m_{chi} for spin-independent effective operators mediating the interaction of the dark matter particles with the qq initial state. The limits are compared with results from the published ATLAS hadronically decaying W/Z and j+chichi searches, CoGeNT, XENON100, and LUX. These limits are shown as they are given in the corresponding publications and are only shown for comparison with our results, since they are obtained assuming the interactions are mediated by operators different from those used for the ATLAS limits.

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Figure 07

Observed 95% C.L. upper limits on the cross section multiplied by the branching ratio of Z->l+l- of the scalar-mediator theory as a function of m_{chi}. The observed cross-section limit for a scalar-mediator mass, m_{eta}, of 1000 GeV is shown. Production cross sections predicted from theory are shown for m_{eta}=1 TeV and for different values of the coupling strength, f.

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Figure 08

Observed 95% C.L. upper limits on the coupling constant, f, of the scalar-mediator theory as a function of m_{chi} and the mediator mass, m_{eta}. The cross-hatching shows the theoretically accessible region outside the range covered by this analysis. The white region is phase space beyond the model's validity. In the excluded region in the upper left-hand corner, demarcated by the black line, the lower limit on f from our relic abundance calculations based on Ref. 45 and 46 is greater than the upper limit measured in this analysis.

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