Fresh Look at Neutrino Self-Interactions With the Lyman-$\hat{I}\pm$ Forest: Constraints from EFT and PRIYA Simulations

Abstract

We present the first search for evidence of neutrino self-interaction with two new, state-of-the-art likelihoods for eBOSS Lyman-$\hat{I}\pm$ data. These are an effective field theory (EFT) likelihood with priors from the Sherwood simulation suite, and a compressed likelihood derived from an emulator built using the PRIYA simulation suite. Previous analyses that combined Planck measurements with eBOSS Lyman-$\hat{I}\pm$ likelihoods based on earlier simulations found a preference for neutrino self-interactions. In contrast, using either of the new eBOSS Lyman-$\hat{I}\pm$ likelihoods, we find that a joint analysis with the cosmic microwave background (CMB) data from Planck prefers a negligible level of neutrino self-interaction, and derive new constraints on the neutrino self-coupling: ${\log }_{10}(G_{\mathrm{eff}}{\mathrm{MeV}}^2)=-5.57_{-0.58}^{+0.98}$ for Planck + EFT Lyman-$\hat{I}\pm$, and ${\log }_{10}(G_{\mathrm{eff}}{\mathrm{MeV}}^2)=-5.16_{-0.67}^{+1.12}$ for Planck + PRIYA Lyman-$\hat{I}\pm$, at 68% confidence. We also consider Planck in combination with DESI BAO data, and find that the latter does not provide significant constraining power for neutrino self-interactions.

20 pages, 7 figures. v2: minor wording changes + additional appendix