Phenomenology of the standard HVM and 95.4 GeV excess

TL;DR

The paper develops the Standard Hierarchical VEV Model (SHVM) as a low-energy realization of the flavor problem framework, embedding hierarchical VEVs of gauge-singlet scalars χ_r within a dark-technicolor context and enforcing a softly broken flavor symmetry $\mathcal{Z}_{\rm N} \times \mathcal{Z}_{\rm M} \times \mathcal{Z}_{\rm P}$ to suppress large FCNCs. It derives the scalar potential, soft-breaking structure, and Yukawa couplings, and constructs collider predictions across HL-LHC, HE-LHC, and future 100 TeV colliders, highlighting a unique signature from the pseudoscalar $a_3$ and a new neutrino-philic dark matter candidate from the axial field $a_7$. The model naturally accommodates a 95.4 GeV di-photon excess via $a_3$ while remaining testable through non-overlapping final states in inclusive production channels, enabling discrimination from other extended scalar sector models. The neutrinic dark matter scenario offers a novel DM candidate that interacts exclusively with neutrino pairs and can be realized via a misalignment mechanism, with the mass scale of $a_7$ controlled by the soft parameters and the UV completion. Overall, the SHVM provides a coherent, testable link between flavor structure, collider phenomenology, and nonstandard dark matter, with concrete predictions for upcoming high-energy colliders.

Abstract

We investigate the collider phenomenology of the standard Hierarchical VEVs Model by proposing a new version, which avoids large flavor changing neutral current interactions, thus, rendering the scale of new physics as low as the electroweak scale. The resulting collider signatures are distinctive and testable at the High-Luminosity LHC, the High-Energy LHC, and future 100\,TeV hadron colliders. Remarkably, one of the pseudoscalars in the model can account for the 95.4\,GeV di-photon excess observed by ATLAS and CMS. In addition, the model naturally accommodates a new class of neutrino-philic dark matter candidate, \emph{neutrinic dark matter}, that interacts exclusively with neutrino pairs.

Figures (17)

• Figure 1: Constraints on the masses of the scalars $m_{h_i}$ and the scale $\Lambda$ from the experimental upper limits of radiative leptonic decay $\mu \rightarrow e\gamma$, as given in the equation \ref{['meg']}. The solid lines represent the allowed regions, while the dashed lines indicate the excluded parameter space.
• Figure 2: Branching ratios of various possible decay modes of the pseudoscalar $a_3$.
• Figure 3: Cross-section ($\sigma \times BR$) for the processes $pp \rightarrow a_3 \rightarrow t \overline{t}$ and $pp \rightarrow a_3 \rightarrow \gamma \gamma$ as functions of the pseudoscalar mass $m_{a_3}$ are shown in figure \ref{['figa3a']} for the 14 TeV HL-LHC, figure \ref{['figa3b']} for the 27 TeV HE-LHC, and in figure \ref{['figa3c']} for a 100 TeV collider, where we have set the scale $\Lambda=500$ GeV.
• Figure 4: The branching ratio of various possible decay modes of the scalar $s_1$, assuming $\Lambda=500$ GeV.
• Figure 5: Cross-section ($\sigma \times BR$) for the processes $pp \rightarrow s_1 \rightarrow ee$ and $pp \rightarrow s_1 \rightarrow \gamma \gamma$ as functions of the scalar mass $m_{s_1}$ are shown in figure \ref{['figh1a']} for the 14 TeV HL-LHC, figure \ref{['figh1b']} for the 27 TeV HE-LHC, and in figure \ref{['figh1c']} for a 100 TeV collider, where the scale $\Lambda=500$ GeV.