The issue of deriving $ZH\eta$ vertex in the simplest little Higgs (SLH) model is revisited. Special attention is paid to the treatment of noncanonically-normalized scalar kinetic matrix and vector-scalar two-point transitions. We elucidate a general procedure to diagonalize a general vector-scalar system in gauge theories and apply it to the case of SLH. The resultant $ZH\eta$ vertex is found to be different from those which have already existed in the literature for a long time. We also present an understanding of this issue from an effective field theory viewpoint.

• Received 10 November 2017
• Revised 22 February 2018

DOI:https://doi.org/10.1103/PhysRevD.97.075005

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Published by the American Physical Society