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Chirality is defined through the ±1 eigenvalue under action of γ^5 on ψ, a Dirac field thus projected into its left- or right-handed component by the projection operators (1−γ^5)/2 or (1+γ^5)/2 on ψ. For massless particles (only!) chirality coincides with [helicity], a notion which is frame-dependent, and hence ambiguous for massive particles. Avoid using the [helicity] tag instead: the projectors *must* be implied.

-1 votes

Spinor components in Dirac Equation are 'coupling'?

I'm not sure what physical intuition you are after about the coupled components of Dirac spinors, which describe a particle and an antiparticle of both spin directions each. The Dirac Equation with yo …
Cosmas Zachos's user avatar
1 vote

Yukawa Interaction with Chiral Fermions

I suspect you are trapped in bad notation, which, sadly, is quite common, even though you appreciate the crucial chirality-flipping $\gamma^0$ involved in the overbar. … My first guess for your two-chirality-flip effective interaction, so, then no chirality-flip interaction, is $$igm\phi\overline{\psi_L}(/\!\!\partial ~/\Box) ~~\psi_L= igm \phi~~\overline{\psi}(/\!\! …
Cosmas Zachos's user avatar
0 votes

Shouldn't there be a Particle for Changing Left-handed to Right-handed Particles and Vice Ve...

I gather you appreciate the crucial difference between chirality & helicity for massive particles, and never use L and R for helicity, which is $\pm$. … chiral projectors slip past the $\gamma^0$ implicit in the overbar and flip to the other kind, enforcing the opposite chirality of the particle destroyed by the term. …
Cosmas Zachos's user avatar
1 vote
Accepted

How is the chirality for the weak interaction conserved for non-relativistic neutrinos?

I am unclear what you are asking, but here is the connection of slow fermions' helicity and chirality. … No, really slow neutrinos produced by weak interactions change chirality, as per above. In their frame, only about half will interact weakly. …
Cosmas Zachos's user avatar
3 votes
Accepted

Higgs Boson and Chirality

point, in that this Higgs particle, h, therefore couples identically to its v.e.v. to the fermions, also linking their chiralities: so, when those fermions emit higgses, virtual or not, flipping their chirality
Cosmas Zachos's user avatar
3 votes
Accepted

The chirality of the standard model fermions

...right-handed neutrinos could be included in the Standard Model by extending the fermion content. But these would be completely neutral under the Group of Standard Model. Why is that a problem? Why …
Cosmas Zachos's user avatar
1 vote
Accepted

Interactions in nonlinear chiral theories

Yes, it is there to ensure that there is no mixing between the singlet, displayed separately, and the octet, so you do not double count. The coefficient of $g_8^M$ contains no singlet. The 3×3 matrix …
Cosmas Zachos's user avatar
1 vote
Accepted

Chiral Lagrangian Field

Is there a meaning to take this field as an exponential function of the generators? From your basic Lie group theory you presumably appreciate the logic of the chiral model of the astounding Gürsey: …
Cosmas Zachos's user avatar
3 votes
Accepted

Does particle parity play any role in matter anti-matter annihilation?

The dominant force in the Standard Model is electromagnetism, by far, a vectorlike interaction which preserves parity, with interaction vertex $$ eA_\mu (\overline {e_L } ~\gamma^\mu e_L + \overline …
Cosmas Zachos's user avatar
10 votes
Accepted

How does changing handedness cause mass?

Chirality is a Lorentz-invariant, mathematical, unintuitive notion: a Dirac fermion ψ, has a L- and a R-chiral piece. Chirality is defined through the operator γ5, which has eigenvalues ±1. … Books describe how chirality is connected to helicity and spin, but you might not need to know the details, if the math cloys you. …
Cosmas Zachos's user avatar
2 votes
Accepted

How is the property of chirality used?

The mass term transitions a propagating particle into one of the opposite chirality, whereas in the absence of this mass term, chirality is preserved. … But the mass term connects the two chiralities, L→R, R→L, so chirality may switch as the fermion travels along. …
Cosmas Zachos's user avatar
1 vote
Accepted

Chirality in muon decay

I would personally use a R subscript for it, to indicate the actual chirality of the particle, and prevent the misreading you evince here, but then I'd confuse others... …
Cosmas Zachos's user avatar
3 votes

Explaining "Left" and "Right" to an Alien using Chirality and Helicity

Chirality is also odd under parity (L is sent to R). …
Cosmas Zachos's user avatar
2 votes
Accepted

Coefficient of effective chiral Lagrangian of $\pi\pi$ scattering

Importantly, observe what you might know, namely the method in the madness of the Lie algebra elements involved, $$L=\frac{F^{2}}{4} \rm{Tr}(\partial_{\mu}U^{\dagger}\partial^{\mu}U)= \frac{F^{2}}{4} …
Cosmas Zachos's user avatar
3 votes

How do massless particles have the same chirality and helicity when they are different prope...

. $$ But this manifestly commutes with chirality, $\gamma^5$, so the two operators share eigenvectors. Left-chiral ones have negative helicity, and right-chiral ones positive helicity. … Note how a fermion reverses chirality, spin and helicity upon charge conjugation. …
Cosmas Zachos's user avatar

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