A minimal set of top-Higgs anomalous couplings

TL;DR

The paper develops a minimal, gauge-invariant effective-field-theory description of top–Higgs interactions by employing equations of motion to derive operator equalities that remove redundant derivative operators. The resulting framework describes off-shell $H f_i f_j$ vertices with only scalar and pseudoscalar structures, and provides explicit, minimal forms for the $Htt$ and $Htq$ couplings, with corrections expressed in terms of dimension-six operator coefficients $C_x$ and the scale $\Lambda$. It also analyzes how these operator replacements affect gauge-boson vertices, finding that the Lorentz structure remains unchanged but the operator count can be reduced in specific channels (notably $Ztq$ from eight to five). The conclusions highlight practical benefits for phenomenology and Monte Carlo event generation, enabling simpler, more constraint-friendly analyses of top–Higgs anomalous interactions while maintaining full gauge invariance.

Abstract

We use the equations of motion to simplify the general form of fermion-fermion-Higgs interactions generated by dimension-six gauge-invariant effective operators. After removing redundant operators it is found that the most general H f_i f_j vertex for off-shell fermions f_i, f_j and an off-shell Higgs boson only involves scalar and pseudo-scalar terms, without derivatives. Examples are presented for the Htt and Htq interactions, where q=u,c, giving the explicit expressions of the vertices in terms of gauge-invariant operators. The new operator equalities obtained here also reduce the number of operators relevant for the Ztq vertices, although the general form of these interactions is not simplified with respect to previous results.

Figures (1)

• Figure 1: Feynman diagrams contributing to $gc \to tH$.