a reference text on how ckm matrix would appear in a part of standard model lagrangian that contains interactions with the W-plus/minus vector gauge bosons involving quarks
https://arxiv.org/abs/1912.09562
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Hollik also discusses ckm matrix... also worth mentioning is the interaction of fermions and higgs boson as contained in eqn(123), pp. 19, "coupling constants proportional to the fermion masses"
https://arxiv.org/abs/1012.3883
so i quite get that in my own discussions here, eqn(20.10.4), or eqn(17.8)
https://foxtrotpaparomeo.wordpress.com/2023/01/11/12012023first-order-calculations-of-the-probability-amplitude-for-higgs-boson-to-electron-positron-decay/