Searching for long-lived axion-like particles via displaced vertices at the HL-LHC

Chong-Xing Yue; Xin-Yang Li; Shuo Yang; Mei-Shu-Yu Wang

doi:10.1140/epjc/s10052-025-15190-x

paper

Searching for long-lived axion-like particles via displaced vertices at the HL-LHC

arXiv:2510.24097 · doi:10.1140/epjc/s10052-025-15190-x

Abstract

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 $s = 14$ TeV and the integrated luminosity $L =$ $3$ ab $^{- 1}$ . We consider the process $pp \to γ a$ with the ALP $a$ decaying into a pair of displaced charged leptons and perform a detailed analysis of two types of signals: $π^{+} π^{-} γ E /_{T}$ and $ℓ^{+} ℓ^{-} γ E /_{T}$ . For the $π^{+} π^{-} γ E /_{T}$ signal, we find that the prospective sensitivities of the HL-LHC can reach $g_{aW W} \in [8.72 \times 1 0^{- 3}, 6.42 \times 1 0^{- 2}]$ TeV $^{- 1}$ for the ALP mass $m_{a} \in [4, 10]$ GeV. While for the $ℓ^{+} ℓ^{-} γ E /_{T}$ signal, the HL-LHC can probe a broader parameter space, with the sensitivities covering $m_{a} \in [4, 10]$ GeV and $g_{aW W} \in [4.17 \times 1 0^{- 3}, 2.00 \times 1 0^{- 1}]$ TeV $^{- 1}$ . 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.

arXiv comment24 pages, 7 figures, accepted for publication in EPJC

Searching for long-lived axion-like particles via displaced vertices at the HL-LHC

Abstract

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