Anomalous couplings in $Z\gamma$ events at NNLO+PS and improving $\nu\bar\nu\gamma$ backgrounds in dark-matter searches

The measurement of the triple gauge couplings (TGCs) is a central part of diboson studies at the LHC. In this letter we consider the $Z\gamma$ process and include anomalous TGCs (aTGCs) in the event generation at next-to-next-to-leading order QCD accuracy (NNLO+PS) within the MiNNLO$_{\rm PS}$ framework. While our implementation is fully general and applies to both $Z\to \ell^+\ell^-$ and $Z\to \nu\bar\nu$ decays, we focus here on the $\nu\bar\nu\gamma$ final state. After validation of our simulation of $\nu\bar\nu\gamma$ events, for which NNLO+PS accuracy is achieved for the first time, the effects of aTGCs on various distributions are studied. Moreover, we show the relevance of NNLO+PS accuracy for the $\nu\bar\nu\gamma$ background to photon plus missing energy signatures in dark-matter searches, and we compare MiNNLO$_{\rm PS}$ predictions for $\nu\bar\nu\gamma$ production to recent 13 TeV data.