Search for heavy resonances decaying to a $Z$ boson and a photon in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper reports a search for heavy resonances decaying into a Z boson and a photon in proton-proton collisions at 13 TeV, setting upper limits on production cross sections for masses between 250 GeV and 2.75 TeV.

Contribution

First search for Z+photon resonances above 250 GeV at 13 TeV with ATLAS, establishing upper limits on production cross sections for new scalar bosons.

Findings

No significant excess observed over background.

Upper limits set on cross section times branching ratio.

Mass range explored from 250 GeV to 2.75 TeV.

Abstract

This Letter presents a search for new resonances with mass larger than 250 GeV, decaying to a $Z$ boson and a photon. The dataset consists of an integrated luminosity of 3.2 fb$^{-1}$ of $pp$ collisions collected at $\sqrt{s} = 13$ TeV with the ATLAS detector at the Large Hadron Collider. The $Z$ bosons are identified through their decays either to charged, light, lepton pairs ($e^+e^-$, $\mu^+\mu^-$) or to hadrons. The data are found to be consistent with the expected background in the whole mass range investigated and upper limits are set on the production cross section times decay branching ratio to $Z\gamma$ of a narrow scalar boson with mass between 250 GeV and 2.75 TeV.