Search for a high mass diphoton resonance using the ATLAS detector

TL;DR

This paper reports a search for high-mass diphoton resonances using ATLAS data, observing a 3.4 sigma deviation in 2015 but no significant excess in 2016, and sets limits on production cross sections.

Contribution

First search for high-mass diphoton resonances with ATLAS at 13 TeV, reporting potential signal hints and setting exclusion limits.

Findings

3.4 sigma deviation at 730 GeV in 2015 data

No significant excess in 2016 data

Limits on resonance production cross section

Abstract

A search for new spin-0 resonances decaying into two photons in the ATLAS experiment at the LHC is described. The analysis is based on $pp$ collision data at $\sqrt{s}$=13 TeV corresponding to integrated luminosities of 3.2/fb and 12.2/fb recorded in 2015 and 2016, respectively. A deviation from the Standard Model background-only hypothesis corresponding to 3.4 standard deviations is observed in the 2015 data for a resonance mass hypothesis of 730 GeV. No significant excess at such mass over the background expectation is observed in the 2016 data. Limits on the production cross section times branching ratio to two photons of such resonances are reported.