Perturbative unitarity constraints on generic Yukawa interactions

We study perturbative unitarity constraints on generic Yukawa interactions where the involved fields have arbitrary quantum numbers under an Pi iSU(N-i) circle times U(1) group. We derive compact expressions for the bounds on the Yukawa couplings for the cases where the fields transform under the trivial, fundamental or adjoint representation of the various SU(N) factors. We apply our results to specific models formulated to explain the anomalous measurements of (g - 2)(mu) and of the charged- and neutral-current decays of the B mesons. We show that, while these models can generally still explain the observed experimental values, the required Yukawa couplings are pushed at the edge of the perturbative regime.

Automated summary

The study focuses on perturbative unitarity constraints on generic Yukawa interactions involving fields with arbitrary quantum numbers under Pi iSU(N-i) circle times U(1) group. Compact expressions for bounds on Yukawa couplings are derived based on how fields transform under different representations of SU(N) factors. The results are applied to specific models explaining anomalous measurements and it is shown that while the models can generally explain observed values, the required Yukawa couplings are pushed to the edge of the perturbative regime.