Observation of tt¯γγ production at √s=13 TeV with the ATLAS detector
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Date
2026
Authors
Aad, G.
Aakvaag, E.
Abbott, B.
Abdelhameed, S.
Abeling, K.
Abicht, N.J.
Abidi, S.H.
Aboelela, M.
Aboulhorma, A.
Abramowicz, H.
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Physics Letters B, 2026; 874:140195-1-140195-19
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Abstract
This paper presents the first observation of top-quark pair production in association with two photons (𝑡̄𝑡𝛾𝛾). The measurement is performed in the single-lepton decay channel using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider. The data correspond to an integrated luminosity of 140 fb−1 recorded during Run 2 at a centre-of-mass energy of 13 TeV. The 𝑡̄𝑡𝛾𝛾 production cross section, measured in a fiducial phase space based on particle-level kinematic criteria for the lepton, photons, and jets, is found to be 2.42+0.58 −0.53 fb, corresponding to an observed significance of 5.2 standard deviations. Additionally, the ratio of the production cross section of 𝑡̄𝑡𝛾𝛾 to top-quark pair production in association with one photon is determined, yielding (3.30+0.70 −0.65) × 10−3
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© CERN for the beneϧt of the ATLAS Collaboration. Published by Elsevier B.V. Funded by SCOAP³. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).