# Thinking about Chirality and Helicity

Here is my point about chirality and helicity:

I thought that chirality is defined for field, But helicity is defined for particle state, you can really measure helicity though measure the spin and momentum.

But as for chirality, it's for field in different rep of Lorentz group. Nothing to do with moving. So for a particle , we can only measure mass(and momentum)and spin (and $z$-compoment of it),but we can't measure the chirality of it, because it's not defined for particle state, but only for field.

Chirality enters the interaction though $H_{I}$. So for particle like electron, if you measure a electron, it will always in weak interaction. am I right?

• How do differentiate between particles and field? – AMS Sep 24 '16 at 8:39
• Field is an operator in Fock space , particle state is a state in Fock space. Field dictate the interaction. particle state feels it. – Xian-Hui Sep 26 '16 at 1:23