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Accepted · first revision · record

Title: Can standard nuclear physics produce the ATOMKI angular excess?
Plain: The extra pairs might come from ordinary nuclear effects, such as interference between different ways an excited nucleus emits a pair, or from the detector response. A complete calculation is needed to decide.
Precise: Compute internal pair creation e+ e- angular correlations for the $8\mathrm{Be}$ $18.15\,\mathrm{MeV}$ ($M1$), $4\mathrm{He}$ $20.21\,\mathrm{MeV}$ ($E0$ and $M0$) and $12\mathrm{C}$ $17.23\,\mathrm{MeV}$ transitions including interference of $E0$, $E1$ and $M1$ multipoles, direct-capture components and ab initio transition form factors, and determine whether they produce peaks near 140 degrees ($8\mathrm{Be}$) or 115 degrees ($4\mathrm{He}$) of the observed size. Answer: yes or no, with the predicted angular distributions.
Settled by: Full-multipole calculations with ab initio form factors compared bin by bin with ATOMKI and MEG II angular distributions after detector simulation.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)