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

## TL;DR

This paper suggests that an unstable sterile neutrino with a mass around 10 MeV could produce additional radiation before Big Bang Nucleosynthesis, potentially resolving the Hubble constant tension between local and early Universe measurements.

## Contribution

It proposes a new sterile neutrino model that can reconcile local and early Universe Hubble constant measurements, with testable predictions for upcoming experiments.

## Key findings

- Sterile neutrino can produce extra radiation before BBN.
- Mass and coupling parameters are within reach of current and future experiments.
- Model alleviates the Hubble tension without conflicting with known physics.

## 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 $\Lambda$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 $\nu_{\tau}$ and/or $\nu_{\mu}$ neutrinos, are within reach of Super-Kamiokande as well as upcoming laboratory experiments such as NA62 and DUNE.