Galactic Center gas clouds and novel bounds on ultralight dark photon, vector portal, strongly interacting, composite, and super-heavy dark matter

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Galactic Center gas clouds and novel bounds on ultralight dark photon, vector portal, strongly interacting, composite, and super-heavy dark matter

Amit Bhoonah, Joseph Bramante, Fatemeh Elahi, and Sarah Schon

Phys. Rev. D 100, 023001 – Published 8 July 2019

Abstract

Cold gas clouds recently discovered hundreds of parsecs from the center of the Milky Way Galaxy have the potential to detect dark matter. With a detailed treatment of gas cloud microphysical interactions, we determine Galactic Center gas cloud temperatures, unbound electron abundances, atomic ionization fractions, heating rates, and cooling rates and find how these quantities vary with metallicity. Considering a number of different dark sector heating mechanisms, we set new bounds on ultralight dark photon dark matter for masses $10^{- 22} - 10^{- 10} eV$ , vector portal dark matter coupled through a sub–mega electron volt mass boson, and up to $1 0^{60} GeV$ mass dark matter that interacts with baryons.

Received 11 January 2019

DOI:https://doi.org/10.1103/PhysRevD.100.023001

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)

Particle astrophysics Particle dark matter

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Amit Bhoonah¹, Joseph Bramante^1,2, Fatemeh Elahi³, and Sarah Schon^1,2

¹The McDonald Institute and Department of Physics, Engineering Physics, and Astronomy, Queen’s University, Kingston, Ontario, K7L 2S8, Canada
²Perimeter Institute for Theoretical Physics, Waterloo, Ontario, N2L 2Y5, Canada
³School of Particles and Accelerators, Institute for Research in Fundamental Sciences IPM, Tehran, Iran

Article Text

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Issue

Vol. 100, Iss. 2 — 15 July 2019

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Images

Figure 1
CLOUDY models from top to bottom for clouds $G 1.4 - 1.8 + 87$ , $G 357.8 - 4.7 - 55$ and $G 1.5 + 2.9 + 1.05$ from [5]. Columns from left to right show the equilibrium cooling rate, temperature, and unbound electron (and hydrogen) number density for a given radial depth into the cloud, as measured from the surface. As detailed in Table 1, the radial depth of these clouds varies from 8-12 parsecs. The solid blue, dashed and dotted orange lines correspond to the C1, C2, and C3 gas cloud models described in Table 1. In the density plots, the solid black line shows the constant hydrogen density.
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Figure 2
Bounds on ultralight dark photons with mass $m$ and kinetic mixing parameter $ε$ , using three cold Galactic Center gas clouds, with parameters given in Table 1, and local dark matter densities according to a generalized NFW profile and projected distances from the Galactic Center detailed at the end of Sec. 2. Readers wishing to rescale these bounds for different dark matter background density models should note that the bound on $ε$ scales as $\frac{1}{ρ_{x}^{2}}$ . Bounds using gas cloud $G 1.4 - 1.8 + 87$ , using the temperature reported in Ref. [5], have been indicated as preliminary; see Sec. 7. Different CMB limits from the decay of dark photons into Standard Model photons are also shown in orange [60]. Bounds from satellite measurements of Jupiter’s magnetic field are given in red [60]. A constraint from heating of the Milky Way’s interstellar medium by dark photons is shown in blue [4]. The same mechanism, but applied to gas clouds with average temperature 137 K ( $G 357.8 - 4.7 - 55$ with an average cooling rate of $3.4 \times 10^{-} 28 erg s^{- 1} {cm}^{- 3}$ ) and 22 K ( $G 1.4 - 1.8 + 87$ with an average cooling rate of $1.9 \times 10^{- 29} erg s^{- 1} {cm}^{- 3}$ ) are shown in purple and black, respectively.
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Figure 3
The constraint on the product of the couplings $κ^{2} α_{D} α_{EM}$ is shown in magenta (regions above each line are excluded), for vector portal dark matter heating of Galactic Center gas clouds with gas cloud parameters given in Table 1 and local dark matter densities according to a generalized NFW profile and projected distances from the Galactic Center detailed at the end of Sec. 2. Readers wishing to rescale these bounds for different dark matter background density models should note that the bound on $κ^{2} α_{D} α_{EM}$ scales as $\frac{1}{ρ_{x}}$ . Bounds using gas cloud $G 1.4 - 1.8 + 87$ , using the temperature reported in Ref. [5], have been indicated as preliminary; see Sec. 7. A few benchmark masses with $m_{A^{'}} ≪ α m_{e}$ are shown. The constraints from the Galactic Center gas cloud apply up to coupling values given in Eqs. (14) and (15). The mass range $m_{A^{'}} ≪ α m_{e}$ is chosen in this figure for ease of comparison with terrestrial experiments (SENSEI [68] and XENON [69]). Other constraints come from the SLAC millicharge search [70] shown in gray, supernova 1987A cooling [71] presented in green, and the stellar cooling [72] shown in red. The constraints on effective relativistic degrees of freedom $N_{eff}$ from BBN and CMB observations [72] are shown in cyan and purple, respectively.
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Figure 4
Constraints on the product of the couplings $κ^{2} α_{D} α_{EM}$ are shown in magenta (regions above each line are excluded), for vector portal dark matter heating of gas clouds with cloud parameters given in Table 1 and local dark matter densities according to a generalized NFW profile and projected distances from the Galactic Center detailed at the end of Sec. 2. Readers wishing to rescale these bounds for different dark matter background density models should note that the bound on $κ^{2} α_{D} α_{EM}$ scales as $\frac{1}{ρ_{x}}$ . Bounds using gas cloud $G 1.4 - 1.8 + 87$ , using the temperature reported in Ref. [5], have been indicated as preliminary; see Sec. 7. A few benchmark masses with $m_{A^{'}} > α m_{e}$ are shown. We note that constraints from the Galactic Center gas cloud are effective up to coupling values given in Eq. (15). Terrestrial direct detection bounds [68, 69] are comparatively weak in this regime. We show the bounds for the two cases of $m_{A^{'}} = 10^{- 7} GeV$ and $m_{A^{'}} = 10^{- 5} GeV$ . For an explanation of the feature apparent at $m_{χ} = 10^{- 4} GeV$ for $m_{A^{'}} = 10^{- 7} GeV$ , see the text. Other bounds (SLAC [70], Supernova [71], $N_{eff}$ from BBN and CMB [72], and stellar constraints [72]) are indicated.
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Figure 5
Existing bounds on the spin-independent dark matter–nucleon scattering cross section are shown, along with bounds derived from cold gas clouds at the Galactic Center, for dark matter masses ranging from mega-electron-volts to $1 0^{32} GeV$ , and local dark matter densities according to a generalized NFW profile and projected distances from the Galactic Center detailed at the end of Sec. 2. Readers wishing to rescale these bounds for different dark matter background density models should note that the bound on $σ_{n x}$ scales as $\frac{1}{ρ_{x}}$ . Bounds using gas cloud $G 1.4 - 1.8 + 87$ , using the temperature reported in Ref. [5] have been indicated as preliminary; see Sec. 7. Note that cold gas cloud bounds can be accurately extrapolated out to approximately $1 0^{60} GeV$ ; we have truncated the plot for the sake of clarity. From left to right, bottom to top, prior bounds on dark matter–baryon scattering shown in gray are as follows. Cosmic-ray accelerated dark matter is excluded by searches at Xenon1T (cr xe) and MiniBoone (cr mini) [119]. Spectral distortions of the cosmic microwave background exclude stronger dark matter–baryon couplings (cmb) [76, 77]. Interstellar gas cooling constraints (ism) were first derived in Ref. [1]. The lower bounds from underground direct detection experiments and particularly XENON1T [91] (underground) are combined with overburden upper bounds which were recently derived and summarized in Ref. [112]. The X-ray Calorimetry Rocket did not observe dark matter events in its calorimeter (xqc) over its 10 min flight [107]. Results from an as-yet-unpublished analysis [103] of Interplanetary Monitoring Platform data [120] are displayed (imp). A charged cosmic-ray search using Skylab’s plastic etch detectors was recast for a dark matter bound in Ref. [121]; this analysis (skylab) was later amended in Ref. [101]. A bound from the longevity of white dwarf stars in the Milky Way is also shown (wd) [122]. Nonobservation of tracks in ancient mica excludes dark matter with mass $1 0^{12} - 10^{26} GeV$ [99, 123, 124].
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