Browsing by Author "Wang, Zeren S."

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    Heavy neutral leptons and top quarks in effective field theory
    (Springer Nature, 2025) Beltrán, Rebeca; Cottin Buracchio, Giovanna Francesca; Günther, Julian; Hirsch, Martin; Titov, Arsenii; Wang, Zeren S.
    We study the phenomenology of heavy neutral leptons (HNLs) at the LHC in effective field theory, concentrating on d = 6 operators with top quarks. Depending on the operator choice and HNL mass, the HNLs will be produced either from proton-proton collisions in association with a single top, or via non-standard decays of top quarks. For long-lived HNLs we estimate the sensitivity reach of different detectors to various operators with top quarks and the HNLs for the high-luminosity phase of the LHC. For certain operators, ATLAS and some far detectors (MATHUSLA and ANUBIS) will be able to probe the associated new-physics scale as large as 12 TeV and 4.5 TeV, respectively, covering complementary HNL-mass ranges.
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    Quark flavor violation and axion-like particles from top-quark decays at the LHC
    (SISSA, Springer, 2024) Cheung, Kingman; Chung, Fei-Tung; Cottin Buracchio, Giovanna Francesca; Wang, Zeren S.
    We study axion-like particles (ALPs) with quark-flavor-violating couplings at the LHC. Specifically, we focus on the theoretical scenario with ALP-top-up and ALP-top-charm interactions, in addition to the more common quark-flavor-diagonal couplings. The ALPs can thus originate from decays of top quarks which are pair produced in large numbers at the LHC, and then decay to jets. If these couplings to the quarks are tiny and the ALPs have O 10 $$ \mathcal{O}(10) $$ GeV masses, they are long-lived, leading to signatures of displaced vertex plus multiple jets, which have the advantage of suppression of background events at the LHC. We recast a recent ATLAS search for the same signature and reinterpret the results in terms of bounds on the long-lived ALP in our theoretical scenario. We find that the LHC with the full Run 2 dataset can place stringent limits, while at the future high-luminosity LHC with 3 ab−1 integrated luminosity stronger sensitivities are expected.