Can standard nuclear physics produce the ATOMKI angular excess?
In plain words
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 statement
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.
What would settle it
Full-multipole calculations with ab initio form factors compared bin by bin with ATOMKI and MEG II angular distributions after detector simulation.
Related problems
- Special case of Origin of the ATOMKI 17 MeV pair-emission anomaly