Search for pairs of highly collimated photon-jets in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

Abstract

Results of a search for the pair production of photon-jets$-$collimated groupings of photons$-$in the ATLAS detector at the Large Hadron Collider are reported. Highly collimated photon-jets can arise from the decay of new, highly boosted particles that can decay to multiple photons collimated enough to be identified in the electromagnetic calorimeter as a single, photonlike energy cluster. Data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.7 fb${}^{-1}$, were collected in 2015 and 2016. Candidate photon-jet pair production events are selected from those containing two reconstructed photons using a set of identification criteria much less stringent than that typically used for the selection of photons, with additional criteria applied to provide improved sensitivity to photon-jets. Narrow excesses in the reconstructed diphoton mass spectra are searched for. The observed mass spectra are consistent with the Standard Model background expectation. The results are interpreted in the context of a model containing a new, high-mass scalar particle with narrow width, $X$, that decays into pairs of photon-jets via new, light particles, $a$. Upper limits are placed on the cross section times the product of branching ratios $\sigma \times \mathcal{B}(X\to aa)\times \mathcal{B}(a\to \gamma \gamma {)}^2$ for 200 GeV $<m_X<$ 2 TeV and for ranges of $m_a$ from a lower mass of 100 MeV up to between 2 and 10 GeV, depending upon $m_X$. Upper limits are also placed on $\sigma \times \mathcal{B}(X\to aa)\times \mathcal{B}(a\to 3{\pi }^0{)}^2$ for the same range of $m_X$ and for ranges of $m_a$ from a lower mass of 500 MeV up to between 2 and 10 GeV.

43 pages in total, author list starting page 27, 10 figures, 4 tables, submitted to PRD. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2017-08

References in corpus (12)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• Parton distributions for the LHC
• New parton distributions for collider physics
• Event generation with SHERPA 1.1
• A parton shower algorithm based on Catani-Seymour dipole factorisation
• Luminosity determination in pp collisions at $\sqrt{s}$ = 8 TeV using the ATLAS detector at the LHC
• Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data
• Search for resonances in diphoton events at $\sqrt{s}$=13 TeV with the ATLAS detector
• Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run-1 data
• Jets and Photons

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• Higgs boson decays into narrow di-photon jets and their search strategies at the Large Hadron Collider
• Geometry of ultraperipheral nuclear collisions
• Search for new resonances decaying to pairs of merged diphotons in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• Investigating Boson Sector in an Extended Standard Model with $U(1{)}_D$ Symmetry
• Constraining Stealth SUSY with illuminated fat jets at the LHC