This is Legacy Physics: Dirac vs. Majorana. A vintage science.beef still trundling on from the 1930s...
"Dirac predicted that, in addition to having opposite charges, antimatter partners should have opposite handedness as well.
"A particle is considered right-handed if its spin is in the same direction as its motion. It is considered left-handed if its spin is in the opposite direction.
"Dirac’s equation allowed for neutrinos and anti-neutrinos to be different particles, and, as a result, four types of neutrino were possible: left- and right-handed neutrinos and left- and right-handed antineutrinos. But if the neutrinos had no mass, as scientists thought at the time, only left-handed neutrinos and right-handed antineutrinos needed to exist."
This is the bit I love and which has had me mentally riffing off n on for a couple hours:
"“When Dirac wrote down his equation, that’s when he learned antiparticles exist,” says André de Gouvêa, a theoretical physicist and professor at Northwestern University. “Antiparticles are a consequence of his equation.”"
The bizarre abstraction - my deliberate misreading - that anti-particles didn't exist before he wrote down his equation. Not that he was first to describe something or shone light on some hitherto-hidden sub-basement of particle-physics - opened up a new line of research - but the idea that he 'created' or summoned them up in some way.
That quantum thing whereby you change the outcome of an experiment or alter a phenomenon by observing it - liking the idea of creating something merely by writing it down. Us writers do that all the time, but what if -- etc.