Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1705.05486

Radiative decays of a singlet scalar boson through vector-like quarks

Yeo Woong Yoon·Kingman Cheung·Sin Kyu Kang·Jeonghyeon Song
View original source ↗Read source document ↗Export metadata ↓

Abstract

If the standard model Higgs boson were much heavier, it would appear as a broad resonance since its decay into a pair of longitudinally polarized gauge bosons is highly enhanced. We study whether the same enhancement happens at loop level in a simple extension of the standard model with a singlet scalar boson $S$. In order to focus on the loop effects, we assume that $S$ does not interact with the standard model particles at tree level. The singlet scalar $S$ is linked to the standard model world by vector-like quarks running in the loop. We introduce three vector-like quark multiplets, an $SU(2)_L$ doublet, an up-type singlet, and a down-type singlet. There are two kinds of loop effects in the $S$ phenomenology, the mixing with the Higgs boson and the radiative decays into $hh$, $WW$, $ZZ$, $gg$, and $γγ$ through the triangle loops. We show that the crucial condition for enhancing loop effects including the longitudinal polarization enhancement is the large mass differences among vector-like quarks. The current LHC constraints on $S$ from the heavy scalar searches and the Higgs precision data are shown to be very significant: the mixing angle with the Higgs boson should be smaller than about 0.1 for $m_S= 750$ GeV.

Explore related subjects

hep-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Yeo Woong Yoon, Kingman Cheung, Sin Kyu Kang, Jeonghyeon Song. 2017-05-15. Radiative decays of a singlet scalar boson through vector-like quarks. https://doi.org/10.1103/physrevd.96.055041

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Sensitivity Analysis of Singlet Vector-Like B Quarks via Photon-Induced and Z-Initiated Processes at FCC-$μp$

This study presents a systematic sensitivity analysis of singlet-type vector-like $B$ quark production at an FCC--$μp$ collider with a centre-of-mass energy of $\sqrt{s}=24.5~\mathrm{TeV}$ through photon- and $Z$-initiated production mechanisms. The analysis focuses on the $B\to Zb$ decay channel, considering the leptonic decay of the $Z$ boson and the hadronic decay of the accompanying $W$ boson, leading to the final state $\ell^+\ell^-bjj$. Detector-resolution effects are incorporated through a simplified Gaussian smearing procedure, and the discovery and exclusion sensitivities are evaluated using an Asimov-based statistical framework. For the photon-induced channel, the most favourable sensitivity is obtained for $R_L=0.05$ and $\mathcal{L}=1000~\mathrm{fb^{-1}}$. Over the mass range $M_B=2$--$3~\mathrm{TeV}$, the expected $5σ$ discovery reach is approximately $g^\ast\simeq0.263$--$0.328$, while the $95\%$ C.L. exclusion sensitivity extends to $g^\ast\simeq0.162$--$0.197$. On the other hand, the $Z$-initiated channel provides a substantially stronger sensitivity and extends the investigated mass range up to $M_B=4.5~\mathrm{TeV}$. For $R_L=0.05$ and $\mathcal{L}=500~\mathrm{fb^{-1}}$, the $5σ$ discovery reach is approximately $g^\ast\simeq0.038$--$0.056$, while the corresponding $95\%$ C.L. exclusion sensitivity reaches $g^\ast\simeq0.021$--$0.032$. These results demonstrate that photon- and $Z$-initiated single production at an FCC--$μp$ collider provide complementary probes of heavy vector-like $B$ quarks. Moreover, the $Z$-initiated channel offers particularly strong sensitivity to small effective couplings in the multi-TeV mass region beyond the present direct LHC reach.

hep-ph↗
arXiv2026

Flavon assisted low scale leptogenesis

Low-scale leptogenesis scenarios, such as the resonant leptogenesis, typically require a highly degenerate mass spectrum of right-handed neutrinos (RHNs). This requirement can be circumvented by extending the seesaw framework with a scalar singlet $S$ that couples to RHNs via the $S N^{}_I N^{}_J$ terms (with $I \neq J$), which opens up new decay channels $N^{}_I \to N^{}_J S$ and provides additional sources of CP violation, thereby enabling successful leptogenesis at the TeV scale without the need for mass degeneracy. In this work, for the first time, we point out that the flavon fields, which are introduced in many flavor-symmetry neutrino mass models to be responsible for the generation of RHN masses through the acquisition of non-zero vacuum expectation values, serve as ideal candidates for the $S$ field. Taking as an example a flavor-symmetry neutrino mass model that naturally realizes the experimentally allowed TM1 mixing pattern and has the attractive features that only one flavon field plays the role of $S$ and that it couples to only two RHNs, we demonstrate that the observed neutrino masses and mixing angles can be consistently reproduced, while the observed baryon asymmetry can be achieved within a parameter space compatible with current experimental constraints.

hep-ph↗
arXiv2026

EasyScan_HEP 2: LLM-Agent Parameter-Scan Workflows in High Energy Physics

Large-language-model (LLM) agents are beginning to reshape the preparation and steering of computational workflows in high-energy physics phenomenology. To accommodate this change, we upgrade EasyScan_HEP to make the construction of parameter-scan configuration files more accessible to LLM-agent assistance. EasyScan_HEP 2 exposes command-line and machine-readable interfaces for LLM-agent workflows, allowing an assistant to translate natural language requests into an explicit .ini configuration that defines the scan method, external-program workflow, constraints, and outputs. The resulting configuration can be inspected through a local Web interface. The framework also supports LLM-agent-guided extension to new scan methods, as illustrated by the integration of BESTFIT, EMCEE, and DYNESTY. In this way, EasyScan_HEP 2 adapts parameter-scan workflows to LLM-agent use while preserving reproducibility, transparency, and user control.

hep-ph↗