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  • Open Access

Tracking axionlike particles at the LHC

Gonzalo Alonso-Álvarez1,2,3, Joerg Jaeckel4, and Diego D. Lopes5

  • 1McGill University Department of Physics & McGill Space Institute, 3600 Rue University, Montréal, Quebec H3A 2T8, Canada
  • 2Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
  • 3Instituto Galego de Física de Altas Enerxías, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain
  • 4Institut für theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg, Germany
  • 5Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André-SP, Brasil

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Phys. Rev. D 114, 015030 – Published 20 July, 2026

DOI: https://doi.org/10.1103/qg9q-dldl

Abstract

Highly boosted axionlike particles decaying into photon pairs are notoriously hard to detect at the LHC. The collimated decay photons cannot be individually reconstructed using only electromagnetic calorimeter information, making the signal less distinguishable from background. In this paper, we propose a search strategy to address this issue, exploiting the fact that a fraction of the decay photons convert into electron-positron pairs inside the tracking detector. The resulting tracks can be resolved with high resolution, making it possible to separate the two collimated photons and resolve a displaced decay vertex. To demonstrate the effectiveness of this approach, we apply it to ALPs in the challenging MeV–GeV range produced via vector boson fusion. We find that such a search could give sensitivity to untested parameter space.

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Phys. Rev. D 114, 015030– Published 20 July, 2026
  • Received 4 October 2023
  • Accepted 1 July 2026
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