Possible Hints of Sterile Neutrinos in Recent Measurements of the Hubble Parameter

Abstract

Local Universe observations find a value of the Hubble constant $H_0$ that is larger than the value inferred from the Cosmic Microwave Background and other early Universe measurements, assuming known physics and the $\hat{I}›$CDM cosmological model. We show that additional radiation in active neutrinos produced just before Big Bang Nucleosynthesis by an unstable sterile neutrino with mass $m_s=$ O(10) MeV can alleviate this discrepancy. The necessary masses and couplings of the sterile neutrino, assuming it mixes primarily with $\hat{I}{½}_{\ddot{I}}„$ and/or $\hat{I}{½}_{\hat{I}}¼$ neutrinos, are within reach of Super-Kamiokande as well as upcoming laboratory experiments such as NA62 and DUNE.

6 pages, 1 figure; v3: published version