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Probing a light scalar boson with a few-MeV proton beam deep underground

Carlo Broggini1, Giuseppe Di Carlo2, Luca Di Luzio1, Denise Piatti3,1, and Claudio Toni4

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Phys. Rev. D 112, 095037 – Published 24 November, 2025

DOI: https://doi.org/10.1103/ms4p-zymy

Abstract

We propose to investigate the production of a light scalar boson ϕ in low-energy proton-nucleus interactions using the 3.5 MV accelerator of the Bellotti Ion Beam Facility, located in the underground Gran Sasso National Laboratory. Nuclear reactions induced by a few-MeV proton beam on suitable target materials can act as a controlled source of ϕ particles. Owing to the deep-underground location, the facility benefits from substantial cosmic-ray shielding, enabling searches for rare processes with minimal background. The produced ϕ particles will be sought with large-volume, low-background detectors already operating or currently under construction at the Gran Sasso National Laboratory. This approach combines a tunable accelerator-based production mechanism with the exceptional sensitivity of underground rare-event searches, offering a novel avenue to probe light scalar bosons beyond the Standard Model.

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Phys. Rev. D 112, 095037– Published 24 November, 2025
  • Received 15 September 2025
  • Accepted 31 October 2025
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