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arXiv · 2305.14166

Dark Sectors with Mass Thresholds Face Cosmological Datasets

Itamar J. Allali·Fabrizio Rompineve·Mark P. Hertzberg
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Abstract

Interacting dark sectors may undergo changes in the number of their relativistic species during the early universe, due to a mass threshold $m$ (similar to changes in the Standard Model bath), and in doing so affect the cosmic history. When such changes occur close to recombination, i.e., for $m\sim (0.1-10)~\text{eV}$, the stringent bound on the effective number of neutrino species, $N_{\text{eff}}$, can be relaxed and the value of the Hubble expansion rate $H_0$ inferred from Cosmic Microwave Background (CMB) observations raised. We search for such sectors (with and without mass thresholds) in the latest cosmological datasets, including the full-shape (FS) of BOSS DR12 galaxy power spectrum. We perform a detailed analysis, accounting for the choice of prior boundaries and additionally exploring the possible effects of dark sector interactions with (a fraction of) the dark matter. We find $ΔN_{\text{eff}}\leq 0.55\, (0.46)$ at 95% C.L. with (without) a mass threshold. While a significantly larger Hubble rate is achieved in this scenario, $H_0=69.01^{+0.66}_{-1.1}$, the overall fit to CMB+FS data does not provide a compelling advantage over the $Λ$CDM model. Furthermore, we find that dark matter interactions with the dark sector do not significantly improve the (matter fluctuations) $S_8$ tension with respect to the $Λ$CDM model. Our work provides model-independent constraints on (decoupled) dark sectors with mass thresholds around the eV scale.

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Itamar J. Allali, Fabrizio Rompineve, Mark P. Hertzberg. 2023-07-26. Dark Sectors with Mass Thresholds Face Cosmological Datasets. https://doi.org/10.1103/physrevd.108.023527

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