Relic neutrino decay solution to the excess radio background

Author:

P. S. Bhupal Dev, Pasquale Di Bari, Ivan Martínez-Soler, Rishav Roshan

Keyword:

High Energy Physics - Phenomenology, High Energy Physics - Phenomenology (hep-ph), Cosmology and Nongalactic Astrophysics (astro-ph.CO), High Energy Physics - Theory (hep-th)

journal:

date:

2023-12-05 00:00:00

Abstract

The excess radio background detected by ARCADE 2 represents a puzzle within the standard cosmological model. There is no clear viable astrophysical solution and, therefore, it might indicate the presence of new physics. Radiative decays of a relic neutrino $\nu_i$ into a sterile neutrino $\nu_{\rm s}$, assumed to be quasi-degenerate, provide a solution that currently evades all constraints posed by different cosmological observations and reproduces very well the ARCADE 2 data. We find a very good fit to the ARCADE 2 data with best fit values $\tau_i = 1.46 \times 10^{21}\,{\rm s}$ and $\Delta m_i = 4.0 \times 10^{-5}\,{\rm eV}$, where $\tau_i$ is the lifetime and $\Delta m_i$ is the mass difference between the decaying active neutrino and the sterile neutrino. On the other hand, if relic neutrino decays do not explain ARCADE 2 data, then these place a stringent constraint $\D m_i^{3/2} \tau_i \gtrsim 2 \times 10^{14}\,{\rm eV}^{3/2}\,{\rm s}$ in the range $1.4 \times 10^{-5} \, {\rm eV} < \D m_i < 2.5 \times 10^{-4}\,{\rm eV}$. The solution also predicts a stronger 21 cm absorption global signal than the predicted one from the $\L$CDM model, with a contrast brightness temperature $T_{21} = -238^{+21}_{-20}\,{\rm mK}$ ($99\%$ C.L.) at redshift $z\simeq 17$. This is in mild tension with the even stronger signal found by the EDGES collaboration, $T_{21} = - 500^{+200}_{-500}\,{\rm mK} $, suggesting that this might have been overestimated, maybe receiving a contribution from some unidentified foreground source.

PDF: Relic neutrino decay solution to the excess radio background.pdf