Radiative corrections to decays of the 125 GeV Higgs boson in the complex Higgs triplet model

TL;DR

This work provides a comprehensive one-loop analysis of radiative corrections to Higgs decays in the complex Higgs triplet model (CHTM), a framework motivated by neutrino mass generation via the Type-II seesaw. It introduces a gauge-invariant, on-shell renormalization scheme implemented with the pinch technique, and includes higher-order QCD effects for loop-induced processes. The authors demonstrate that Higgs decay rates and branching ratios can deviate from SM predictions by several percent, with characteristic patterns that distinguish the CHTM from other extended-Higgs scenarios, especially in $h\to ZZ^*$, $WW^*$, and $h\gamma\gamma$ channels, and predict sizable effects on the Higgs self-coupling. The results, implemented in H-COUP, have significant implications for HL-LHC and future Higgs-factory measurements, providing concrete targets to test exotic Higgs sectors and the underlying neutrino-mass mechanism.

Abstract

The extension of the Higgs sector with an additional complex triplet field is often considered for generating the neutrino mass by the Type-II seesaw mechanism. Such an extension generally predicts $ρ\neq1$, where $ρ$ is the electroweak rho parameter at the tree level, so that the renormalization of the electroweak parameters is different from models like the standard model (SM) and two Higgs doublet models. In this paper, we present a full set of radiative corrections to decays of the 125 GeV Higgs boson ($h$) in this model. One-loop contributions of the extra Higgs bosons as well as SM fermions and gauge bosons to the decay rates of $h$ are calculated in the on-shell scheme. Gauge dependence appearing in the counter terms of mixing angles is eliminated by the pinch technique. Higher-order QCD corrections are also implemented. We find that the decay rates can significantly deviate from the predictions in the SM and other extensions such as the two Higgs doublet models and the singlet model. For example, the decay rates of $h\to WW^\ast$ and $h\to ZZ^\ast$ can be a few percent larger than the SM value under current experimental and theoretical constraints. In this case, deviations in $h\to γγ$ and Higgs self-coupling can reach about $-20\%$ and $100\%$, respectively. The pattern of the deviations is different from the other extended Higgs models. These characteristic predictions are expected to be detected at the High-Luminosity LHC or future Higgs factories.

Figures (40)

• Figure 1: Diagrams dependent on the gauge parameters $\xi_V^{}$ for the self-energy of the CP-even Higgs bosons.
• Figure 2: Diagrams dependent on the gauge parameters $\xi_V^{}$ for two-point functions of the CP-even Higgs bosons in the $f\bar{f}\to f\bar{f}$ scattering.
• Figure 3: Diagrams dependent on the gauge parameters $\xi_V^{}$ for the self-energy of the CP-odd Higgs bosons.
• Figure 4: Diagrams dependent on the gauge parameters $\xi_V^{}$ for two-point functions of the CP-odd scalar bosons in the $f\bar{f}\to f\bar{f}$ scattering.
• Figure 5: Momentum assignment for the $hf\bar{f}$ vertex (left) and the $hVV\, (h\mathcal{V}\mathcal{V'})$ vertex (right).