absent in dark matter production at the LHC. Addressing the importance of higher dimensional operators will be left to a subsequent publication [^1].

This note focuses on including the $Z$ in the EFT for dark matter at the LHC, and estimates analytically the consequences of including the lowest dimension operators allowing dark matter interactions with the $Z$ [^2]. Section \[sec:EFT\] outlines a peculiar choice of operators for the $Z$ vertex; they are proportional to the momentum-transfer-squared. This choice appears convenient, because the effects of the $Z$ are therefore absent in direct detection. Section \[sec:LHC\] estimates the impact of cancellations between $Z$ exchange and dark matter contact interactions with quarks at the LHC, and section \[sec:DD\] recalls the direct detection bounds.

EFT, assumptions and operators  {#sec:EFT}
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The low energy consequences of New Physics from above a scale $\Lambda$ can be parametrised by contact interactions of coefficient $C/\Lambda^n$. Unitarity [@unitarity1; @unitarity2] approximately implies that $C< 4\pi$, and the contact interaction approximation implies that the momentum exchange should be less than $\Lambda$. This means that an experiment can [*exclude*]{} &gt; &gt; [sensitivity]{}  , \[plage\] where $\hat{s}$ is the four-momentum-squared of the process. Low energy experiments, where $\hat{s} \to 0$, therefore can be 