
New evidence supporting the existence of the hypothetic X17 particle - slowenough
https://arxiv.org/abs/1910.10459
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PaulHoule
It seems strange at first that a particle with a mass of 17 MeV (much less
than a proton) would have gone unnoticed, but the particle they describe is
protophobic, that is, it doesn't couple to protons, so it wouldn't show up in
p-p accelerator experiments.

In nucleon interactions you would have neutrons around which would interact
with protophobic particles.

What I still don't get is why the X17 doesn't show up in e-e colliders. (An X
boson couples to both leptons and quarks, which is why it can contribute to
proton decay)

A protophobic X boson would not contribute to proton decay which could explain
why proton decay is not observed.

