protophobic X boson:
They found that, to be consistent with everything we have seen in experiments designed to characterise the known forces of nature, [this hypothetical dark photon] must interact not with protons and electrons, as a conventional photon does, but with the neutrons inside the beryllium nuclei. This is a property beyond the scope of physics as we know it, which might explain how the particle slipped by unseen in previous dark matter searches. Feng’s team call the interloper a “protophobic X boson“. [NewScientist, 27 August 2016, paywall]
Possibly seen while firing protons at a thin sheaf of lithium-7 in order to make unstable beryllium-8, which then decayed with unexpected results. Only neutrons, huh? This will be interesting if it’s confirmed.
