Self-interacting dark matter without prejudice

Open Access

Self-interacting dark matter without prejudice

Nicolás Bernal, Xiaoyong Chu, Suchita Kulkarni, and Josef Pradler

Phys. Rev. D 101, 055044 – Published 31 March 2020

Abstract

The existence of dark matter particles that carry phenomenologically relevant self-interaction cross sections mediated by light dark sector states is considered to be severely constrained through a combination of experimental and observational data. The conclusion is based on the assumption of specific dark matter production mechanisms such as thermal freeze-out together with an extrapolation of a standard cosmological history beyond the epoch of primordial nucleosynthesis. In this work, we drop these assumptions and examine the scenario from the perspective of the current firm knowledge we have results from direct and indirect dark matter searches and cosmological and astrophysical observations, without additional assumptions on dark matter genesis or the thermal state of the very early universe. We show that even in the minimal setup, where dark matter particles self-interact via a kinetically mixed vector mediator, a significant amount of parameter space remains allowed. Interestingly, however, these parameter regions imply a metastable, light mediator, which in turn calls for modified search strategies.

Received 23 December 2019
Accepted 13 March 2020

DOI:https://doi.org/10.1103/PhysRevD.101.055044

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 Particle dark matter

Particles & Fields

Authors & Affiliations

Nicolás Bernal ^1,*, Xiaoyong Chu ^2,†, Suchita Kulkarni^2,‡, and Josef Pradler^2,§

¹Centro de Investigaciones, Universidad Antonio Nariño, Carrera 3 Este # 47A-15, Bogotá, Colombia
²Institute of High Energy Physics, Austrian Academy of Sciences, Nikolsdorfer Gasse 18, 1050 Vienna, Austria

^*nicolas.bernal@uan.edu.co
^†xiaoyong.chu@oeaw.ac.at
^‡suchita.kulkarni@oeaw.ac.at
^§josef.pradler@oeaw.ac.at

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Issue

Vol. 101, Iss. 5 — 1 March 2020

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Images

Figure 1
DM self-scattering cross section per DM mass, $σ_{χ χ} / m_{χ}$ , as a function of $α_{χ}$ , for $m_{χ} = 10 GeV$ and $m_{V} = 0.1 GeV$ , for a relative DM velocity $v = 10 km / s$ . The horizontal dashed line corresponds to $σ_{χ χ} / m_{χ} = 1 {cm}^{2} / g$ . The vertical dotted line ( $α_{χ} ≃ 1.3 \times 10^{- 2}$ ) depicts the first solution where the latter value of the self-scattering cross section is met.
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Figure 2
Contours of minimal values of $α_{χ}$ satisfying Eq. (2), i.e., implying a phenomenologically relevant DM self-scattering cross section. Shaded regions show the bounds from perturbatively (dark shading), stability of DM halos (medium shading), and cluster bounds (light shading).
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Figure 3
Contours of maximally allowed values of the kinetic mixing parameter $ε$ from a combination of current DM direct detection data, for DM-nucleon scattering [91, 92, 93, 94] in the left panel and DM-electron scattering [95, 96, 97, 98] in the right panel.
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Figure 4
Summary of existing constraints of the dark photon $[ε, m_{V}]$ parameter space. The various labels summarize principal detection strategies, astrophysical constraints from stellar energy loss (“stellar”) [119], and diffuse $γ$ -ray background (“diffuse”) [120], from cooling of the proto-neutron star of SN1987A (“SN”) [124], from beam-dump and collider experiments; see e.g., [125, 126] and references therein. Hatched regions show recent exclusions derived from gamma-ray signatures from SN [127] (blue) and energy-transfer argument inside SN [128] (pink). In addition, contours of mediator lifetime $τ_{V}$ equal to 1 sec (BBN), $10^{13} \sec$ (CMB), as well as $t_{U}$ (universe) are shown. The vertical dashed gray line corresponds to $m_{V} = 2 m_{e}$ . Additional cosmological constraints from Big Bang Nucleosynthesis (BBN) and CMB for $m_{V} > 1 MeV$ are not shown, as they rely on a $V$ abundance created at $T > 1 MeV$ [121].
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Figure 5
Maximum values of $ε$ allowed from CMB observations [137, 138, 139] (left panel) and isotropic gamma-rays [142, 143] (right panel). Below the solid gray line no bounds can be extracted as Eq. (11) is always satisfied. The horizontal gray dashed line marks $m_{V} = 2 m_{e}$ .
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Figure 6
Combination of upper limits on $ε$ presented in Figs. 3 and 5 (left panel) and combination of constraints in Figs. 3, 4, 5 (right panel). At each point $(m_{χ}, m_{V})$ the maximum permissible value of $ε$ has been chosen, $ε = \min {ε_{i}}$ . The enormous range in $ε$ as seen from the color legend is owed to the fact that the direct (Fig. 3) and cosmological constraints (Fig. 5) apply to largely complementary regions in parameter space with significantly different sensitivity to the value of $ε$ (left panel); this sensitivity is altered for $m_{V} < 1 MeV$ once constraints from Fig. 4 are taken into account (right panel).
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