Sensitivity targets for dark photon searches in charged kaon decays
Abstract
We investigate the prospects for detecting invisible dark photons in charged kaon decays through the two-pion channel K+→π+π0 γD and the one-pion radiative decay K+→π+γ γD, where γ and γD denote the ordinary photon and dark photon, respectively. The former decay was previously proposed as a golden channel for massless dark photon searches at NA62, while here we introduce the radiative process as a complementary probe and extend both analyses to massive dark photons. The three-body modes are particularly relevant at low dark photon masses, where the two-body decay K+→π+ γD becomes strongly suppressed and vanishes in the massless limit. For massless dark photons, renormalizable interactions induced by kinetic mixing are absent, and the dominant contribution arises from the effective non-renormalizable flavor-changing quark interaction s→ d γD mediated by a dimension-five magnetic-dipole operator. This is also true for massive dark photons. Their kinetic mixing contributes negligibly to these channels, after considering the existing bounds on the mixing parameter. Only the same flavor changing magnetic-dipole operator as in the massless case is relevant. Using the chiral quark model, we estimate the relevant hadronic matrix elements of the dipole operator and account for constraints from K+→π+ X, where X denotes resonant missing energy, K+→π+νν̅, and K0 − K̅0 mixing. Based on these calculations, we determine the allowed branching ratios for these decay modes and the sensitivities required at NA62 and future charged-kaon facilities.
Related
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BibTeX
@misc{fabbrichesi2026sensitivity,
title = {{Sensitivity targets for dark photon searches in charged kaon decays}},
author = {M. Fabbrichesi and E. Gabrielli and K. Müürsepp},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.08911},
eprint = {2610.08911},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.08911},
}
RIS
TY - UNPB
TI - Sensitivity targets for dark photon searches in charged kaon decays
AU - M. Fabbrichesi
AU - E. Gabrielli
AU - K. Müürsepp
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.08911
UR - https://arxiv.org/abs/2610.08911
AB - We investigate the prospects for detecting invisible dark photons in charged kaon decays through the two-pion channel K^+→π^+π^0 γ_D and the one-pion radiative decay K^+→π^+γ γ_D, where γ and γ_D denote the ordinary photon and dark photon, respectively. The former decay was previously proposed as a golden channel for massless dark photon searches at NA62, while here we introduce the radiative process as a complementary probe and extend both analyses to massive dark photons. The three-body modes are particularly relevant at low dark photon masses, where the two-body decay K^+→π^+ γ_D becomes strongly suppressed and vanishes in the massless limit. For massless dark photons, renormalizable interactions induced by kinetic mixing are absent, and the dominant contribution arises from the effective non-renormalizable flavor-changing quark interaction s→ d γ_D mediated by a dimension-five magnetic-dipole operator. This is also true for massive dark photons. Their kinetic mixing contributes negligibly to these channels, after considering the existing bounds on the mixing parameter. Only the same flavor changing magnetic-dipole operator as in the massless case is relevant. Using the chiral quark model, we estimate the relevant hadronic matrix elements of the dipole operator and account for constraints from K^+→π^+ X, where X denotes resonant missing energy, K^+→π^+νν̅, and K^0 − K̅^0 mixing. Based on these calculations, we determine the allowed branching ratios for these decay modes and the sensitivities required at NA62 and future charged-kaon facilities.
ER -