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

TL;DR

This paper advances the simulation of $Z o uar u\, ext{and}\, Z o \, ext{leptons}$ processes at NNLO+PS accuracy, incorporating anomalous TGCs, and improves background modeling for dark matter searches at the LHC.

Contribution

It introduces a fully general NNLO+PS simulation framework for $Z\, ext{and}\, uar u\, ext{final states with anomalous TGCs, validated against recent data, enhancing background estimates in dark matter searches.

Findings

NNLO+PS accuracy achieved for $ uar u\, ext{final state}$.

Anomalous TGC effects significantly impact distribution shapes.

Improved background modeling for dark-matter searches.

Abstract

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.