A search is presented for a heavy scalar (H) or pseudo-scalar (A) predicted by the two-Higgs-doublet models, where the H/A is produced in association with a top-quark pair (tt¯H/A), and with the H/A decaying into a tt¯ pair. The full LHC Run 2 proton–proton collision data collected by the ATLAS experiment is used, corresponding to an integrated luminosity of 139fb-1. Events are selected requiring exactly one or two opposite-charge electrons or muons. Data-driven corrections are applied to improve the modelling of the tt¯+jets background in the regime with high jet and b-jet multiplicities. These include a novel multi-dimensional kinematic reweighting based on a neural network trained using data and simulations. An H/A-mass parameterised graph neural network is trained to optimise the signal-to-background discrimination. In combination with the previous search performed by the ATLAS Collaboration in the multilepton final state, the observed upper limits on the tt¯H/A→tt¯tt¯ production cross-section at 95% confidence level range between 14 fb and 5.0 fb for an H/A with mass between 400 GeV and 1000 GeV, respectively. Assuming that both the H and A contribute to the tt¯tt¯ cross-section, tanβ values below 1.7 or 0.7 are excluded for a mass of 400 GeV or 1000 GeV, respectively. The results are also used to constrain a model predicting the pair production of a colour-octet scalar, with the scalar decaying into a tt¯ pair.

Search for tt¯H/A→tt¯tt¯ production in proton–proton collisions at s=13 TeV with the ATLAS detector / Zwalinski, L., Zou, W., Zormpa, O., Zorbas, T.G., Zoch, K., Zoccoli, A., Zivkovic, L., Ziolkowski, M., Zinsser, J., Zimine, N.I., Zhukov, K., Zhuang, X., Zhu, Y., Zhu, Y., Zhu, X., Zhu, J., Zhu, C.G., Zhou, Y., Zhou, Y., Zhou, Y., et al.. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - 85:5(2025). [10.1140/epjc/s10052-025-14041-z]

Search for tt¯H/A→tt¯tt¯ production in proton–proton collisions at s=13 TeV with the ATLAS detector

Iuppa R.;Follega F. M.;
2025-01-01

Abstract

A search is presented for a heavy scalar (H) or pseudo-scalar (A) predicted by the two-Higgs-doublet models, where the H/A is produced in association with a top-quark pair (tt¯H/A), and with the H/A decaying into a tt¯ pair. The full LHC Run 2 proton–proton collision data collected by the ATLAS experiment is used, corresponding to an integrated luminosity of 139fb-1. Events are selected requiring exactly one or two opposite-charge electrons or muons. Data-driven corrections are applied to improve the modelling of the tt¯+jets background in the regime with high jet and b-jet multiplicities. These include a novel multi-dimensional kinematic reweighting based on a neural network trained using data and simulations. An H/A-mass parameterised graph neural network is trained to optimise the signal-to-background discrimination. In combination with the previous search performed by the ATLAS Collaboration in the multilepton final state, the observed upper limits on the tt¯H/A→tt¯tt¯ production cross-section at 95% confidence level range between 14 fb and 5.0 fb for an H/A with mass between 400 GeV and 1000 GeV, respectively. Assuming that both the H and A contribute to the tt¯tt¯ cross-section, tanβ values below 1.7 or 0.7 are excluded for a mass of 400 GeV or 1000 GeV, respectively. The results are also used to constrain a model predicting the pair production of a colour-octet scalar, with the scalar decaying into a tt¯ pair.
2025
5
Zwalinski, L.; Zou, W.; Zormpa, O.; Zorbas, T. G.; Zoch, K.; Zoccoli, A.; Zivkovic, L.; Ziolkowski, M.; Zinsser, J.; Zimine, N. I.; Zhukov, K.; Zhuang...espandi
Search for tt¯H/A→tt¯tt¯ production in proton–proton collisions at s=13 TeV with the ATLAS detector / Zwalinski, L., Zou, W., Zormpa, O., Zorbas, T.G., Zoch, K., Zoccoli, A., Zivkovic, L., Ziolkowski, M., Zinsser, J., Zimine, N.I., Zhukov, K., Zhuang, X., Zhu, Y., Zhu, Y., Zhu, X., Zhu, J., Zhu, C.G., Zhou, Y., Zhou, Y., Zhou, Y., et al.. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - 85:5(2025). [10.1140/epjc/s10052-025-14041-z]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/466765
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