According to the Standard Model, the matter and antimatter versions of these mesons should give birth to such daughters in the same proportions.

ECONOMIST: Are matter and antimatter truly opposites?

K-mesons, implied that matter and antimatter are not truly symmetrical.

ECONOMIST: Particle physics

B-mesons to turn into their antimatter counterparts and back again, a process known as mixing.

ECONOMIST: Cosmology and particle physics

Since the predicted decay patterns of the two mesons were a result of the ways that matter and antimatter blended in them, that suggested that those substances are not quite equal and opposite after all.

ECONOMIST: What��s the matter?

Mesons measured by LHCb have already hinted at an answer, and Prof Parkes says that is the next target.

BBC: LHC's D-meson study wraps up antimatter 'flip' story

The new paper represents the last of the four mesons that had never been seen flipping from matter to antimatter and back in a single measurement.

BBC: LHC's D-meson study wraps up antimatter 'flip' story