https://doi.org/10.1140/epjc/s10052-025-15190-x
Regular Article - Theoretical Physics
Searching for long-lived axion-like particles via displaced vertices at the HL-LHC
1
Department of Physics, Liaoning Normal University, 116029, Dalian, China
2
Center for Theoretical and Experimental High Energy Physics, Liaoning Normal University, 116029, Dalian, China
a
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Received:
12
August
2025
Accepted:
10
December
2025
Published online:
19
December
2025
Axion-like particles (ALPs) are well-motivated extensions of the standard model (SM) that appear in numerous new physics scenarios. In this paper, we concentrate on searches for long-lived ALPs predicted by the photophobic scenario at the HL-LHC with the center-of-mass energy 
TeV and the integrated luminosity 
We consider the process 
with the ALP a decaying into a pair of displaced charged leptons and perform a detailed analysis of two types of signals: 
and 
For the 
signal, we find that the prospective sensitivities of the HL-LHC can reach ![$$g_{aWW}\in [8.72 \times 10^{-3}, 6.42 \times 10^{-2}]$$](/articles/epjc/abs/2025/12/10052_2025_Article_15190/10052_2025_Article_15190_tex_eq7.png)
for the ALP mass ![$$m_a \in [4, 10]$$](/articles/epjc/abs/2025/12/10052_2025_Article_15190/10052_2025_Article_15190_tex_eq9.png)
GeV. While for the 
signal, the HL-LHC can probe a broader parameter space, with the sensitivities covering GeV and ![$$g_{aWW} \in [4.17 \times 10^{-3}, 2.00 \times 10^{-1}]$$](/articles/epjc/abs/2025/12/10052_2025_Article_15190/10052_2025_Article_15190_tex_eq12.png)
These long-lived searches complement some previous prompt decay studies from LEP and LHC experiments, extending the parameter space explored by the LHCb collaboration. Our results show that the HL-LHC has significant potential to probe long-lived ALPs via their displaced vertex signatures.
© The Author(s) 2025
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Funded by SCOAP3.
