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A direct measurement of the Higgs-top Yukawa coupling is essential for testing the Standard Model and probing new physics. The associated production of a Higgs boson with a top-quark pair (ttH) provides the only direct access to this coupling at the LHC, with the multilepton channel regarded as the ‘golden channel’ for ttH measurement owing to its relatively high signal-to-background ratio and large Higgs decay ratio. However, this measurement faces a series of challenges including an extremely low production rate and high irreducible backgrounds. The most recent measurement of ttH in the multilepton final states by the ATLAS experiment yields a signal significance of 3.3σ. This analysis uses proton-proton collision data at √s = 13.6 TeV collected by the ATLAS detector during LHC Run 3, with an expected integrated luminosity of 350 fb-1. By incorporating advanced machine learning techniques such as Graph Neural Networks, a precise measurement of the ttH production cross-section can be performed. The analysis aims to surpass the 5σ significance milestone in the multi-lepton channel for the first time, achieving the observation of the ttH process in this channel at the ATLAS experiment. Furthermore, with the precise measurement of the ttH cross-section, the predictions of the Standard Model can be strictly tested.
| 请选择分会 | TeV物理和超出标准模型新物理 |
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