Existence of a 17 MeV boson coupled to electrons · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Existence of a 17 MeV boson coupled to electrons
Plain
If the X17 particle exists, it should also appear when positrons hit electrons at just the right energy. Dedicated experiments are scanning this energy.
Precise · changed · core
Revision 1: Test for a vector or axial-vector boson with $m_X = 16.5 \text{ to } 17.2\,\mathrm{MeV}$ and electron coupling $\epsilon$ of roughly $2e-4 \text{ to } 1.4e-3$ through resonant $e+ e- \to X \to e+ e-$ production (PADME), electron beam-dump and pair-spectrometer experiments. Answer: discovery, or exclusion at 90 percent confidence of the full coupling range implied by the ATOMKI 8Be and 4He rates.
Revision 2: Test for a vector or axial-vector boson with $m_X = 16.5 \text{ to } 17.2\,\mathrm{MeV}$ and electron coupling $\epsilon$ of roughly $2 \times 10^{-4} \text{ to } 1.4 \times 10^{-3}$ through resonant $e+ e- \to X \to e+ e-$ production (PADME), electron beam-dump and pair-spectrometer experiments. Answer: discovery, or exclusion at 90 percent confidence of the full coupling range implied by the ATOMKI 8Be and 4He rates.
Settled by
A further PADME run at higher statistics and an independent resonant-production or beam-dump experiment covering the full coupling range.
Kind
well-posed
Answer type
yes-no
References
(empty)
Literature status
contested
Status note
PADME (arXiv 2505.24797, 2025) found an excess near 16.90 MeV with a global significance of about 2 standard deviations; no follow-up result had been published, to our knowledge, as of mid-2026.
Posed since
2016

Decisions