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## Main Question or Discussion Point

Suppose I couple a fermion field to a scalar field using [itex]\mathrm{i} g \bar{\psi}\psi \varphi [/itex] and [itex]\mathrm{i} g \bar{\psi}\gamma_5\psi\varphi[/itex].

I'm trying to understand what would be the physical difference between these interactions. I know that [itex](1/2)(1\pm \gamma_5)[/itex] approximately projects out the left and right handed components of Dirac fields and that this is related to the fact that the weak interaction couples preferentially to left-handed particles and right-handed anti-particles, but other than that I'm pretty clueless.

I'm trying to understand what would be the physical difference between these interactions. I know that [itex](1/2)(1\pm \gamma_5)[/itex] approximately projects out the left and right handed components of Dirac fields and that this is related to the fact that the weak interaction couples preferentially to left-handed particles and right-handed anti-particles, but other than that I'm pretty clueless.

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