Higgs boson decays $h\rightarrow Z \gamma$ and $h\rightarrow m_V Z$ in the $U(1)_X$VLFM

TL;DR

This paper investigates how a $U(1)_X$ extended model with vectorlike fermions can alter Higgs decay rates to $Z ext{ }\gamma$ and vector meson plus $Z$, potentially revealing new physics effects.

Contribution

It introduces a $U(1)_X$VLFM model that predicts measurable deviations in Higgs decay rates due to new fermions and their mixing with SM particles.

Findings

Deviations in $h o Z ext{ }\gamma$ decay rates can be significant.

Altered $h o m_V Z$ decay rates suggest new physics signals.

Loop corrections involving new particles impact Higgs couplings.

Abstract

We study the Higgs boson decays $h \to Z\gamma$ and $h \to m_VZ$ in a model with vectorlike fermions and $U(1)_X$ symmetry ($U(1)_X$VLFM), where $m_V$ is a vector meson ($\rho,\ \omega,\ \phi,\ J/\psi,\ \Upsilon$). The exotic Yukawa interactions in this model generate mixing between Standard Model (SM) fermions and vectorlike fermions, and this mixing affects the Higgs boson mass and Higgs couplings. The corrections to the CP-even and CP-odd $h\gamma Z$ couplings come from loop diagrams that involve the new particles, and these corrections have a clear impact on the decay rates of $h\to Z\gamma$ and $h\to m_VZ$. In suitable regions of the parameter space, the model can produce non-negligible deviations in $\Gamma_{\rm NP}(h\to Z\gamma)/\Gamma_{\rm SM}(h\to Z\gamma)$ and $\Gamma_{\rm NP}(h\to m_VZ)/\Gamma_{\rm SM}(h\to m_V Z)$, providing possible signals of new physics (NP) beyond the SM.