Exploring the Higgs Portal with 10/fb at the LHC

TL;DR

This work investigates how new exotic scalars coupled to the SM through the Higgs portal can alter Higgs production and decay, thereby impacting LHC Higgs searches. It uses both a model-independent effective-field-theory framework with operator coefficients $c_G$ and $c_\gamma$ and explicit Higgs-portal scalar models across multiple SM representations to quantify modifications to gluon-fusion production and the diphoton decay channel. The authors analyze two scenarios: a light SM-like Higgs near 124–126 GeV with possible NP-enhanced diphoton rates, and a heavier Higgs that could be hidden by NP that suppresses gluon fusion; they map the allowed parameter spaces and compare with direct scalar searches. They conclude that current data strongly constrain NP contributions to gluon fusion for a light Higgs, while heavy-Higgs hiding remains viable in certain regions; direct scalar searches provide complementary tests and future data will probe much of the remaining parameter space.

Abstract

We consider the impact of new exotic colored and/or charged matter interacting through the Higgs portal on Standard Model Higgs boson searches at the LHC. Such Higgs portal couplings can induce shifts in the effective Higgs-gluon-gluon and Higgs-photon-photon couplings, thus modifying the Higgs production and decay patterns. We consider two possible interpretations of the current LHC Higgs searches based on ~ 5/fb of data at each detector: 1) a Higgs boson in the mass range (124-126) GeV and 2) a `hidden' heavy Higgs boson which is underproduced due to the suppression of its gluon fusion production cross section. We first perform a model independent analysis of the allowed sizes of such shifts in light of the current LHC data. As a class of possible candidates for new physics which gives rise to such shifts, we investigate the effects of new scalar multiplets charged under the Standard Model gauge symmetries. We determine the scalar parameter space that is allowed by current LHC Higgs searches, and compare with complementary LHC searches that are sensitive to the direct production of colored scalar states.

Figures (5)

• Figure 1: Constraints on the coefficients of the effective operators $c_G$ and $c_\gamma$. In the left panel we show constraints from the ATLAS data for a 126 GeV Higgs boson. In the right panel we show constraints from the CMS data for a 124 GeV Higgs boson. In each panel, we show the confidence levels of 1$\sigma$ (orange), 2$\sigma$ (yellow), 3$\sigma$ (solid boundary). We also show contours of constant gluon fusion Higgs production cross section normalized to the SM value (blue) and the normalized rate of the $\gamma \gamma$ channel (red). Solid lines show twice the SM rate, while dashed lines show one half the SM rate. The green dot indicates the SM ($c_G = c_\gamma = 0$)
• Figure 2: Values of the coefficient $c_G$ as a function of Higgs mass for which the Higgs boson production cross section is sufficiently suppressed for it to be hidden from current LHC searches (Orange). We also show the contours of constant cross section in the gluon fusion channel relative to its SM value: twice (solid), one half (dashed), and one tenth (dotted) the SM values.
• Figure 3: Scenario A: Constraints on the coupling $\lambda$ and the mass $m_S$ of the colored scalars. In the left panels, we show constraints coming from ATLAS with the Higgs mass fixed to be 126 GeV, while in the right panels we show constraints coming from CMS with the Higgs mass fixed to be 124 GeV. The $1\sigma$ (orange) and the $2\sigma$ (yellow) allowed regions are presented for the representations $({\bf 3}, {\bf 1}, -\frac{4}{3})$ (top pannels) and $({\bf 8}, {\bf 2}, \frac{1}{2})$ (bottom panels). Finally the solid lines bound the $3\sigma$ allowed regions.
• Figure 4: Constraints on the coupling $\lambda$ and the mass $m_S$ of the color neutral scalars. In the left panel, we show constraints coming from ATLAS with the Higgs mass fixed to be 126 GeV, while in the right panel we show constraints coming from CMS with the Higgs mass fixed to be 124 GeV. The $1\sigma$ (orange) and the $2\sigma$ (yellow) allowed regions are presented for the $({\bf 1}, {\bf 1}, 2)$ representation. Finally the solid line bounds the $3\sigma$ allowed region.
• Figure 5: Regions of scalar parameter space that allow a heavy Higgs boson to be consistent with existing LHC searches. In the left panel we present the allowed region in the $m_h - m_S$ plane with $\lambda = -1$, while in the right panel we present the region in the $m_S - \lambda$ plane for a 300 GeV Higgs boson. We show the results for two representations: $({\bf 3}, {\bf 2}, \frac{1}{6})$ (green) and $({\bf 8}, {\bf 2}, \frac{1}{2})$ (blue). We also show with dashed lines the corresponding estimate of the current LHC bounds from $(jj)(jj)$ searches: color octets between 200 and 300 GeV and color triplets below 300 GeV are still allowed (see next Section for details).