Vector Higgs-portal dark matter and the invisible Higgs

TL;DR

The paper investigates vector dark matter that couples to the Standard Model through a renormalizable Higgs portal, realized via Stückelberg or hidden-Higgs mechanisms and stabilized by a natural $Z_2$ symmetry. It shows that vector DM can be compatible with WMAP and XENON100 constraints while significantly enhancing the Higgs invisible width, potentially hiding the Higgs at the LHC. The analysis combines relic abundance, direct detection, and collider constraints, highlighting that BR$(h\to XX)$ can be large for light Higgs but remains constrained for heavier Higgs, with a viable window around 230–250 GeV when BR$^{inv}$ is substantial. The work also contrasts the vector case with scalar Higgs-portal DM, noting both similarities and important differences in Higgs decays and unitarity considerations. Future experiments like XENON1T and continued LHC analyses will probe most of the model’s parameter space.

Abstract

The Higgs sector of the Standard Model offers a unique probe of the hidden sector. In this work, we explore the possibility of renormalizable Higgs couplings to the hidden sector vector fields which can constitute dark matter (DM). Abelian gauge sectors with minimal field content, necessary to render the gauge fields massive, have a natural Z_2 parity. This symmetry ensures stability of the vector fields making them viable dark matter candidates, while evading the usual electroweak constraints. We illustrate this idea with the Stueckelberg and Higgs mechanisms. Vector DM is consistent with the WMAP, XENON100, and LHC constraints, while it can affect significantly the invisible Higgs decay. Due to the enhanced branching ratio for the Higgs decay into the longitudinal components of the vector field, the vector Higgs portal provides an efficient way to hide the Higgs at the LHC. This could be the reason why the latest combined ATLAS/CMS data did not bring evidence for the existence of the Higgs boson.

Figures (5)

• Figure 1: Feynman diagrams for DM annihilation (left), direct detection (center) and invisible Higgs decay (right).
• Figure 2: Parameter space allowed by WMAP (between the "gull--shaped" curves) and XENON100 for $m_h = 150$ GeV, and prospects for XENON1T.
• Figure 3: Branching ratio for the Higgs invisible decay as a function of the Higgs mass (top) and the dark matter mass (bottom). The scan is over ($m_h$, $m_X$, $\lambda_{hv}$) and subject to the WMAP and XENON100 constraints.
• Figure 4: Branching ratio for the invisible Higgs decay as a function of the Higgs mass (top) and the dark matter mass (bottom). The scan is over ($m_h$, $m_X$, $\lambda_{hv}$) and subject to the WMAP, XENON100 and ATLAS/CMS constraints.
• Figure 5: Branching ratio for the invisible Higgs decay into scalars as a function of the Higgs mass (top) and the dark matter mass (bottom). The scan is over ($m_h$, $m_S$, $\lambda_{hs}$) and subject to the WMAP, XENON100 and ATLAS/CMS constraints.