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arXiv · 2103.03249

The Hubble Tension as a Hint of Leptogenesis and Neutrino Mass Generation

Miguel Escudero·Samuel J. Witte
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Abstract

The majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $H_0$ tension, however only if one introduces additional dark radiation at the level of $ΔN_{\rm eff} \sim 0.5$. We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $H_0$ observed by the SH$_0$ES collaboration is expected to occur at the level of $\sim 10\%$ in the primordial majoron cosmology (to be compared with $\sim 0.1\%$ in the case of $Λ$CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $H_0$.

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Miguel Escudero, Samuel J. Witte. 2021-06-17. The Hubble Tension as a Hint of Leptogenesis and Neutrino Mass Generation. https://doi.org/10.1140/epjc%2Fs10052-021-09276-5

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