Quantum Electrodynamics – Are There Any Right Chiral Isolated Electron Particles in Nature?

chiralityelectronshiggsquantum-electrodynamicsstandard-model

Note: I refrain from using the concept of handedness and the terms left-handed and right-handed when referring to chirality since these usually refer to the helicity of charged fermions and their antiparticles and prefer to use instead the terms referring to their Lorentz invariant but not a constant of motion chirality, namely as Left-Chiral and Right-Chiral similar as looking statically at your two hands without any momentum involved. These handedness above terms sometimes used in common for either referring to helicity or chirality I find a big source of confusion even for the related WP pages references.

My question is:

It is stated in WP Chiral Theories,

"Particle physicists have only observed or inferred left-handed
fermions and right-handed antifermions engaging in the charged weak
interaction."

In the above quote WP uses the terms left-handed and right-handed referring to the chirality of these particles… ):

Since a right-chiral fermion would not carry any weak hypercharge thus it does not interact with the Higgs that would strongly imply that this electron does not gain any mass from the Higgs field. The same is also true for a left-chiral antifermion like a left-chiral positron (i.e. only right-chiral positrons carry a weak hypercharge).

But a massless electron cannot be described anymore as a physical electron.

Therefore I'm asking are there actually in nature any right-chiral isolated electrons or is this just a mathematical induced physics effective theory used in order to describe the Higgs mechanism?

Best Answer

I would strongly disfavor your associating handedness with helicity instead of chirality, but no matter... Indeed, the WP usage of right-handed for right-chiral (annihilated by $1-\gamma_5$) is fine. It is a source of clarity, not confusion. In this issue, helicity stays out of the picture, regardless of language.

Since a right-chiral fermion would not carry any weak hypercharge thus it does not interact with the Higgs that would strongly imply that this electron does not gain any mass from the Higgs field....

Right-chiral fermion fields have a hypercharge proportional to their electric charge, by the (EWeak) Gell-Mann—Nishijima formula. They do interact with the Higgs field, in the Yukawa terms of vanishing total weak hypercharge. These terms couple right-chiral to left-chiral fermions and induce the fermion masses through the v.e.v. of the Higgs field, of course. (Charged current weak interactions refer to W couplings, and not Higgs couplings.)

Right-chiral electrons exist, and they are, on average, half the degrees of freedom my and your and the universe's electrons have.

They are never isolated, as the electron mass connects them to their left-chiral brothers. Chirality is not constant in time. They have little to do with the Higgs mechanism. (I hope you don't actually mean SSB, instead).


NB There is a pedagogical picture presenting this as a chirality oscillation controlled by the mass term in the hamiltonian. A stationary solution of the free Dirac equation dictates immediately, starting from the R state, $$ \langle \gamma_5 \rangle = \cos(2mt). $$