- #1

ChrisVer

Gold Member

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## Main Question or Discussion Point

Why can't there be a term in the SM lagrangian for the U(1)_Y of the form:

[itex] F_{\mu \nu} \tilde{F}^{\mu \nu} [/itex] ?

As there is for the strong interactions?

(Although I've seen such terms appearing in the axion models, such as the KSVZ where by introducing an additional very heavy quark Q with charge [itex]e_Q[/itex], you can have the coupling of the axion field [itex]\alpha[/itex] with light quarks via the EM anomalies: [itex] L_{EM-anom} = \frac{a}{f_a} 3 e_Q^2 \frac{\alpha_{fine-str}}{4 \pi} F_{\mu \nu} \tilde{F}^{\mu \nu} [/itex] )

[itex] F_{\mu \nu} \tilde{F}^{\mu \nu} [/itex] ?

As there is for the strong interactions?

(Although I've seen such terms appearing in the axion models, such as the KSVZ where by introducing an additional very heavy quark Q with charge [itex]e_Q[/itex], you can have the coupling of the axion field [itex]\alpha[/itex] with light quarks via the EM anomalies: [itex] L_{EM-anom} = \frac{a}{f_a} 3 e_Q^2 \frac{\alpha_{fine-str}}{4 \pi} F_{\mu \nu} \tilde{F}^{\mu \nu} [/itex] )