Accidental suppression of Wilson coefficients in Higgs coupling

A bstract Higgs couplings are essential probes for physics beyond the Standard Model (BSM) since they can be modified by new physics, such as through the Higgs portal interaction $$ {\left|H\right|}^2\mathcal{O} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mfenced> <mml:mi>H</mml:mi> </mml:mfenced> <mml:mn>2</mml:mn> </mml:msup> <mml:mi>O</mml:mi> </mml:math> . These modifications influence Higgs interactions via dimension-6 operators of the form ( ∂ | H | 2 ) 2 and | H | 6 , which are generally expected to be of comparable size. This paper discusses a phenomenon of accidental suppression, where the | H | 6 coupling is significantly smaller than ( ∂ | H | 2 ) 2 . This suppression, arising from the truncation of the tree-level effective potential, lacks a clear symmetry explanation but persists in portal models. This paper aims to inspire further studies on additional instances of accidental suppression without symmetry explanations or a general framework to characterize such suppression. We also discuss constraints, at the HL-LHC and future colliders, on the Wilson coefficients of the two dimension-6 operators for various benchmark scenarios of the concrete model.