Axion-Higgs portal

Open Access

Axion-Higgs portal

Martin Bauer, Guillaume Rostagni, and Jonas Spinner

Phys. Rev. D 107, 015007 – Published 6 January 2023

Abstract

The phenomenology of axions and axionlike particles strongly depends on their couplings to Standard Model particles. The focus of this paper is the phenomenology of the unique dimension-six operator respecting the shift symmetry: the axion-Higgs portal. We compare constraints from Higgs physics, flavor-violating and radiative meson decays, bounds from atomic spectroscopy searching for fifth forces, and astrophysical observables. In contrast to the QCD axion, axions interacting through the axion-Higgs portal are stable and can provide a dark matter candidate for any axion mass. We derive the parameter space for which freeze-out and freeze-in production, as well as the misalignment mechanism, can reproduce the observed relic abundance and compare the results with the phenomenological constraints. For comparison, we also derive Higgs, flavor, and spectroscopy constraints, and the parameter space for which the scalar Higgs portal without derivative interactions can explain dark matter.

Received 5 August 2022
Accepted 21 October 2022

DOI:https://doi.org/10.1103/PhysRevD.107.015007

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Dark matter

Axions Higgs bosons

Particles & Fields

Authors & Affiliations

Martin Bauer ¹, Guillaume Rostagni ¹, and Jonas Spinner ^1,2

¹Institute for Particle Physics Phenomenology, Department of Physics, Durham University, Durham DH1 3LE, United Kingdom
²Institut für Theoretische Teilchenphysik, Universität Karlsruhe, Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany

Article Text

Click to Expand

References

Click to Expand

Issue

Vol. 107, Iss. 1 — 1 January 2023

Reuse & Permissions

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Diagrams for different processes induced by the axion-Higgs portal. (a) Higgs decay into two axions. (b) Contribution to the flavor changing transition $s \to d a a$ . (c) Contribution to the vector meson annihilation $V \to γ a a$ . (d) Contribution to the potential between electrons and nuclei generated by the exchange of axion pairs.
Reuse & Permissions
Figure 2
Constraints and projections from Higgs and flavor-violating meson decays and bounds from supernova energy loss for the axion-Higgs portal (left) and the Higgs portal (right). The color coding is indicated in the right panel. For the parameter space above the black solid line in the left panel, the approximate shift symmetry is not a good assumption anymore, whereas the region above the black line in the right panel violates perturbativity. Note that these bounds are also relevant for lower values of $m_{a}$ for the case of the axion-Higgs portal, whereas cosmological constraints become stronger for the Higgs portal; see also Fig. 4. The supernova bound is taken from [56].
Reuse & Permissions
Figure 3
Bounds on the axion coupling and scale obtained from spectroscopic data for the axion-Higgs (left) and scalar Higgs (right) portals. The red bound is obtained from low- $ℓ$ hydrogen states with a cutoff $r_{C} = r_{p}$ ; the dashed lines show the dependence of this bound on the chosen cutoff. In blue are the cutoff-independent bounds obtained from $ℓ = 3$ hydrogen f-states. The bounds shown indicate the relative strength and cutoff dependence of the spectroscopy searches. Most of the parameter space would be excluded by perturbativity or shift-symmetry-breaking operators with $m_{a} ≳ f$ as shown in Fig. 2.
Reuse & Permissions
Figure 4
On the left, we show the required couplings for the axion-Higgs portal to explain the observed value for the energy density of dark matter $Ω h^{2} = 0.12$ [62] for various mechanisms. On the right, we show the corresponding situation for the Higgs portal; the supernova and Eot-Wash bounds are taken from [56]. The orange lines for freeze-out production are an estimate for a smooth intersection between the regimes that are dominated by $b \bar{b} \leftrightarrow a a$ and $γ γ \leftrightarrow a a$ . For the case of freeze-in production, we show several lines to visualize the dependence on the cutoff temperature $T_{R}$ . The blue regions visualize where freeze-in production is possible.
Reuse & Permissions
Figure 5
We visualize the effects of the dependence of freeze-in production on the cutoff temperature $T_{R}$ . The left panel is complementary to the left panel of Fig. 4, where we now vary $T_{R}$ for some fixed values of $m_{a}$ . The right panel shows the various contributions to the relic abundance in dependence of $T_{R}$ .
Reuse & Permissions
Figure 6
Like Fig. 5, but for the Higgs portal. The wiggles in the $γ γ \to s s$ line at high values of $T_{R}$ are due to numerical instabilities; however, one can analytically show that this contribution is subleading in the limit of large cutoff temperatures. Depending on the value of the mass of the scalar $m_{s}$ , stronger bounds on $c_{s h}$ might apply; this can be seen in Fig. 4.
Reuse & Permissions

Physical Review D

covering particles, fields, gravitation, and cosmology