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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Search for a resonance decaying into a scalar particle and a Higgs boson in the final state with two bottom quarks and two photons with 199 fb-1 of data collected at √s=13 and 13.6 TeV with the ATLAS detector. Phys. Lett. B, 877, 140425–19pp.
Abstract: A search for the resonant production of a heavy scalar X decaying into a lighter scalar S and a Higgs boson, through the process X -> S(-> b (b) over bar )H(-> gamma gamma), where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using integrated luminosities of 140 and 59 fb(-1) of proton-proton collision data at centre-of-mass energies of 13 and 13.6 TeV, respectively, recorded with the ATLAS detector at the LHC. The search is performed over the mass ranges of 170 <= m(X) <= 1000 GeV and 15 <= m(S) <= 500 GeV. No significant excess over the Standard Model background predictions is observed and limits at 95% confidence level are set on the product of cross section and branching fraction for the process X -> S(-> b (b) over bar )H(-> gamma gamma) at 13 TeV, ranging from 9 fb to 0.06 fb.
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Melini, D. (2026). Top-quark physics: from Run 2 to the HL-LHC. Eur. Phys. J. Plus, 141(6), 698–5pp.
Abstract: The top quark is a fundamental particle of the standard model and plays an important role in beyond the standard model scenarios. The status of top-quark measurements by ATLAS and CMS is summarized, reporting new recent measurements of top-quark cross sections and top-quark properties. The future high-luminosity run of the Large Hadron Collider is foreseen to produce a huge dataset where top quarks can be studied in detail. The latest projections on expected results on top-quark physics in future high-luminosity runs of the Large Hadron Collider are presented, and the impact of such future measurements on testing the standard model consistency and on constraining new physics scenarios is evaluated.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Characterization of nuclear breakup as a function of hard-scattering kinematics using dijets measured by ATLAS in p plus Pb collisions. Phys. Lett. B, 877, 140440–18pp.
Abstract: This Letter analyzes the sensitivity of event geometry estimators to the initial-state kinematics of hard scattering in proton-lead collisions. This analysis uses dijets as a proxy for the parton-parton scattering configuration, correlating it with event geometry estimators, namely the energy deposited in the Zero-Degree Calorimeter and the transverse energy recorded in the Forward Calorimeter in the Pb-going direction. The analysis uses data recorded by the ATLAS detector at the Large Hadron Collider with a nucleon-nucleon center-of-mass energy of 8.16 TeV, corresponding to an integrated luminosity of 56 nb(-1). The jets are measured within the pseudorapidity interval -2.8 < eta < 4.5, where positive eta values correspond to the direction of the proton beam. Results are presented as a function of the Bjorken-x of the parton originating from the proton, x(p). Both event geometry estimators are found to be dependent on x(p), with the energy deposited in the Zero-Degree Calorimeter about six times less sensitive to x(p) compared with the transverse energy deposited in the Forward Calorimeter.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Search for the Higgs boson decay to a Z boson and a photon in pp collisions at √s=13 TeV and 13.6 TeV with the ATLAS detector. Phys. Lett. B, 876, 140313–21pp.
Abstract: A search for the Higgs boson decay to a.. boson and a photon in the ll gamma (l = e, mu) final state is performed using root s collisions at root s = 13.6 TeV recorded with the ATLAS detector at the Large Hadron Collider during 2022-2024, corresponding to an integrated luminosity of 165 fb(-1). The signal yield, normalised to the Standard Model prediction, is measured to be μ= 0.9(-0.6)(+0.7), compatible with the expected value of μ= 1.0 +/- 0.7. This corresponds to an observed (expected) signal significance of 1.4 (1.5) standard deviations under the background-only hypothesis. This result is combined with that of a similar search performed with 140 fb(-1) of root s = 13 TeV pp collisions to provide the best expected sensitivity to date to this rare decay, namely an observed (expected) signal strength of μ= 1.3(-0.5)(+0.6) (mu = 1.0(-0.5)(+0.6)), corresponding to an observed (expected) significance of 2.5 (1.9) standard deviations. The measurement is consistent with the Standard Model expectation.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Bouchhar, N., Cabrera Urban, S., Cantero, J., et al. (2026). Study of Higgs boson pair production in the HH → b(b)over-barγγ final state with 308 fb-1 of data collected at √s=13 TeV and 13.6 TeV by the ATLAS experiment. Phys. Lett. B, 876, 140280–21pp.
Abstract: A search for Higgs boson pair production in the b (b) over bar gamma gamma final state is performed. The proton-proton collision dataset corresponds to an integrated luminosity of 308 fb-1, consisting of two samples, 140 fb(-1) at a centre-of-mass energy of root s = 13 TeV and 168 fb(-1) at root s = 13.6 TeV, recorded between 2015 and 2024 by the ATLAS detector at the CERN Large Hadron Collider. In addition to a larger dataset, this analysis improves upon the previous search in the same final state through several methodological and technical developments. The Higgs boson pair production cross section divided by the Standard Model prediction is found to be mu(HH) = 0.9(-1.1)(+1.4) (mu(HH) = 1(-1.0)(+1.3) expected), which translates into a 95% confidence-level upper limit of mu(HH) < 3.7. At the same confidence level the Higgs self-coupling modifier is constrained to be in the range -1.6 < kappa(lambda) < 6.6 (-1.8 < kappa(lambda) < 6.9 expected).
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