Measurement of the $Z\gamma\rightarrow\nu\bar{\nu}\gamma$ production cross section in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector and limits on anomalous triple gauge-boson couplings

TL;DR

This paper measures the production rate of Z bosons with an associated photon in proton-proton collisions at 13 TeV, using ATLAS data, and sets limits on possible new physics in gauge-boson interactions.

Contribution

First measurement of $Z ightarrow uar{ u}$ with a photon at 13 TeV, including limits on anomalous gauge couplings using ATLAS data.

Findings

Measured $Z ightarrow uar{ u}\gamma$ cross section as a function of photon $E_T$.

No evidence of anomalous triple gauge-boson couplings was found.

Set upper limits on $ZZ\gamma$ and $Z\gamma\gamma$ couplings.

Abstract

The production of $Z$ bosons in association with a high-energy photon ($Z\gamma$ production) is studied in the neutrino decay channel of the $Z$ boson using $pp$ collisions at $\sqrt{s}$ = 13 TeV. The analysis uses a data sample with an integrated luminosity of 36.1 fb$^{-1}$ collected by the ATLAS detector at the LHC in 2015 and 2016. Candidate $Z\gamma$ events with invisible decays of the $Z$ boson are selected by requiring significant transverse momentum ($p_{T}$) of the dineutrino system in conjunction with a single isolated photon with large transverse energy ($E_{T}$). The rate of $Z\gamma$ production is measured as a function of photon $E_{T}$, dineutrino system $p_{T}$ and jet multiplicity. Evidence of anomalous triple gauge-boson couplings is sought in $Z\gamma$ production with photon $E_{T}$ greater than 600 GeV. No excess is observed relative to the Standard Model expectation, and upper limits are set on the strength of $ZZ\gamma$ and $Z\gamma\gamma$ couplings.