For a massive fermion, show that handedness is not a good quantum number. That is, show that γ^5

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Step 1: **Define the Hamiltonian and $gamma^5$**
The Dirac Hamiltonian for a massive fermion in

For a massive fermion, show that handedness is not a good quantum number. That is, show that $\gamma^5$ does not commute with the Hamiltonian. However, verify that helicity is conserved but is frame dependent. In particular, show that the helicity is reversed by "overtaking" the particle concerned.