# Search for new phenomena in events with at least three photons collected in $pp$ collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector

Abstract : Results of a search for new phenomena in events with at least three photons are reported. Data from proton--proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb$^{-1}$, were collected with the ATLAS detector at the LHC. The observed data are well described by the Standard Model. Limits at the 95% confidence level on new phenomena are presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay $Z\to 3\gamma$, as well as di-photon and tri-photon resonance searches. For a Standard Model Higgs boson decaying to four photons via a pair of intermediate pseudoscalar particles ($a$), limits are found to be $\sigma \times {\text {BR}}(h \rightarrow aa) \times {\text {BR}}(a \rightarrow \gamma \gamma)^{2} < 10^{-3} \sigma_{\text{SM}}$ for 10 GeV $< m_{a} <$ 62 GeV. Limits are also presented for Higgs boson-like scalars ($H$) for $m_{H} >$ 125 GeV, and for a $Z'$ decaying to three photons via $Z' \rightarrow a+\gamma \rightarrow 3\gamma$. Additionally, the observed limit on the branching ratio of the $Z$ boson decay to three photons is found to be BR$(Z \rightarrow 3\gamma) < 2.2 \times 10^{-6}$, a result five times stronger than the previous result from LEP.
Type de document :
Article dans une revue
European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2016, 76, pp.210. 〈10.1140/epjc/s10052-016-4034-8〉

http://hal.in2p3.fr/in2p3-01201767
Contributeur : Emmanuelle Vernay <>
Soumis le : vendredi 18 septembre 2015 - 08:16:31
Dernière modification le : lundi 22 octobre 2018 - 09:42:01

### Citation

G. Aad, S. Albrand, J. Brown, J. Collot, S. Crépé-Renaudin, et al.. Search for new phenomena in events with at least three photons collected in $pp$ collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2016, 76, pp.210. 〈10.1140/epjc/s10052-016-4034-8〉. 〈in2p3-01201767〉

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