Observational constraints on decoupled hidden sectors

Matti Heikinheimo, Tommi Tenkanen, Kimmo Tuominen, and Ville Vaskonen

Phys. Rev. D 94, 063506 – Published 8 September 2016; Erratum Phys. Rev. D 96, 109902 (2017)

Abstract

We consider an extension of the Standard Model with a singlet sector consisting of a real (pseudo)scalar and a Dirac fermion coupled with the Standard Model only via the scalar portal. We assume that the portal coupling is weak enough for the singlet sector not to thermalize with the Standard Model allowing the production of singlet particles via the freeze-in mechanism. If the singlet sector interacts with itself sufficiently strongly, it may thermalize within itself, resulting in dark matter abundance determined by the freeze-out mechanism operating within the singlet sector. We investigate this scenario in detail. In particular, we show that requiring the absence of inflationary isocurvature fluctuations provides lower bounds on the magnitude of the dark sector self-interactions and in parts of the parameter space favors sufficiently large self-couplings, supported also by the features observed in the small-scale structure formation.

Received 13 April 2016

DOI:https://doi.org/10.1103/PhysRevD.94.063506

Physics Subject Headings (PhySH)

Extensions of Higgs sector Extensions of fermion sector Particle astrophysics Particle dark matter

Particles & Fields

Erratum

Erratum: Observational constraints on decoupled hidden sectors [Phys. Rev. D 94, 063506 (2016)]

Matti Heikinheimo, Tommi Tenkanen, Kimmo Tuominen, and Ville Vaskonen

Phys. Rev. D 96, 109902 (2017)

Authors & Affiliations

Matti Heikinheimo^1,2,*, Tommi Tenkanen^1,2,†, Kimmo Tuominen^1,2,‡, and Ville Vaskonen^3,2,§

¹Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
²Helsinki Institute of Physics, P.O. Box 64, FI-00014 Helsinki, Finland
³University of Jyvaskyla, Department of Physics, P.O.Box 35 (YFL), FI-40014 University of Jyvaskyla, Finland

^*matti.heikinheimo@helsinki.fi
^†tommi.tenkanen@helsinki.fi
^‡kimmo.i.tuominen@helsinki.fi
^§ville.vaskonen@jyu.fi

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Vol. 94, Iss. 6 — 15 September 2016

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Images

Figure 1
The portal coupling that yields the correct dark matter abundance as a function of the dark matter self-coupling for $m_{s} = 0.1 GeV$ , in the thermal i.e. dark freeze-out scenario (dashed line) and in the nonthermal i.e. in the standard freeze-in scenario (dotted horizontal line). The solid diagonal line is the critical value for thermalization of the dark sector.
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Figure 2
The self-coupling as a function of the dark matter mass required to obtain the correct relic abundance for $λ_{hs} = 1 0^{- 12}$ , (solid black line) $λ_{hs} = 1 0^{- 11}$ (dashed black line), $λ_{hs} = 1 0^{- 10}$ (dotted black line) and $λ_{hs} = 1 0^{- 9}$ (dot-dashed black line). In the blue shaded region the freeze-out happens at a (semi)relativistic temperature, in the red shaded region we find no solutions to obtain the observed dark matter abundance, and in the lower white region the dark matter abundance can be obtained via the standard freeze-in scenario.
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Figure 3
The Yukawa coupling as a function of the fermion mass required to obtain the correct relic abundance for $λ_{hs} = 1 0^{- 12}$ , (solid black line) $λ_{hs} = 1 0^{- 11}$ (dashed black line), $λ_{hs} = 1 0^{- 10}$ (dotted black line) and $λ_{hs} = 1 0^{- 9}$ (dot-dashed black line) assuming $m_{s} = 10 m_{ψ}$ . The color coding of the shaded regions is the same as in Fig. 2. Below the solid, dashed and dotted red contours the dark sector thermalizes via scalar self-scattering before the scalars have decayed to fermions, for $λ_{s} = 0.1$ , 0.01 and 0.001, respectively.
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Figure 4
Upper panel: if the fermion Yukawa coupling is very small, the particle production is dominated by the dark freeze-out of the scalar abundance (blue thick curve). As $2 m_{ψ} \leq m_{s}$ these will ultimately decay to fermions and the dark freeze-in will provide only a subleading contribution to the fermion abundance (red thin curve). Lower panel: as the Yukawa coupling increases, but is not strong enough for the fermions to thermalize, the dark freeze-in production (red thin curve) is more important than the contribution from the scalar freeze-out (blue thick curve).
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Figure 5
The self-interaction bound and isocurvature constraints for the scalar dark matter scenario. The self-interaction limit, $σ_{DM} / m_{DM} < 1 {cm}^{2} / g$ , is shown by the yellow shaded region in the top left corner together with the $σ_{DM} / m_{DM} = 10$ , $0.1 {cm}^{2} / g$ contours (dashed and dotted, respectively), and the isocurvature constraints by the gray contours for $H_{*} = 1 0^{13}$ , $1 0^{12}$ , $1 0^{11}$ , $1 0^{10} GeV$ from left to right. The area to the right of each contour is ruled out for the given value of the inflationary scale $H_{*}$ . The blue and red shaded regions and the black lines correspond to those in Fig. 2.
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Figure 6
Same as Fig. 5 for the case of fermion dark matter, for $m_{s} = 10 m_{ψ}$ . The red contour marks the thermalization via scalar self-scattering for $λ_{s} = 0.1$ as in Fig. 3, and $λ_{s} = 0.01$ has been used for the isocurvature contours.
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