CERN Accelerating science

The LHCb experiment searches for low-mass dilepton resonances that could be due to mediators between the Standard Model and a hypothesized dark sector, which interacts feebly through kinetic mixing. Results from Run 2, focusing on prompt and displaced dimuon decays, have set world-leading exclusion limits on masses down to the dimuon kinematic threshold. This poster presents prospects to search for dilepton resonances below 100 MeV with the Upgraded LHCb detector using excited D meson decays to a D meson and a dielectron pair. We exploit the upgraded detector’s capabilities to detect displaced D meson decays at the first trigger level and to reconstruct soft electrons to collect a large number of these decays, several orders of magnitude larger than previous experiments. Ongoing efforts, based on 2024 data, aim to use this unique dataset to test dark photon models as well as protophobic models that could explain the X17 anomaly observed in ATOMKI experiments.

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Submitted by lhcb.secretariat@cern.ch