Were electrons initially left-handed, as neutrinos still are today?

Question

These days, neutrinos are left-handed, just as they were a long time ago. These days electrons are right- as well as left-handed. Were they only left-handed a long time ago, before having interacted with any force field?

I can imagine that neutrinos still are left-handed today as they barely reacted with matter. Electrons have reacted though, and maybe they have developed a right-handed portion well as a left-handed portion. They don't move at lightspeed anymore (so at lightspeed after just after creation).

Before the Higgs field became effective, all particles moved at the speed of light. Wouldn't the theory be more symmetric if besides left-handed neutrinos, also one-chirality electrons were created? Or is a theory with two chiralities from the start more symmetric (for both the electron and the neutrino)?

Answer 1

A massive particle in its rest frame is equal parts left- and right-handed. There is a correlation between chirality and spin which appears at high momentum; chirality is a frame-dependent observable.

The weak charged current (associated with the $W$ bosons) is a mechanism for interactions between the left-handed parts of matter particles and the right-handed parts of antimatter particles. The products of charged weak decays therefore tend to be polarized, with the polarization stronger if the decay is more energetic. That's why, for instance, the pseudoscalar pion prefers $\pi^+\to\mu^+\nu_\mu$ over $\pi^+\to e^+\nu_e$, even though the latter would liberate much more energy: the charged lepton has to be polarized the "wrong way" to make the final state spinless.

The polarization of beta-electrons was actually discovered in the 1920s by Cox and collaborators, who were doing some of the earliest experiments on Mott scattering and discovered that they needed to use a thermal electron source rather than a beta emitter for their "control" experiment to give a null result. The significance of the discovery was not understood until the fall of parity in 1957.

Neutrinos and electrons are both equal parts left- and right-handed in their rest frames. The difference is that, because the electron is more massive and participates in electromagnetism, it's much easier to interact with an electron so that its rest frame is the same as your rest frame.