Resonant neutrino self-interactions: Insights from the full shape galaxy power spectrum

Abstract

This paper investigates resonant neutrino self-interactions in cosmology by employing, for the first time, the effective field theory of large-scale structure to model their impact on the matter distribution up to mildly nonlinear scales. We explore a broad range of mediator masses in two main analyses: one combining BOSS Full Shape (FS) galaxy clustering with Big Bang Nucleosynthesis (BBN), and another combining FS with Planck Cosmic Microwave Background (CMB) data. Our results place the strongest cosmological constraints to date on the resonant self interactions when using FS+Planck data, reaching up to $g_ν< 10.8 \times 10^{-14}$ at $95\%$ confidence for the 1 eV mediator. Notably, FS+BBN can constrain the interaction for the 10 eV mediator independently of CMB data, yielding $g_ν< 7.33 \times 10^{-12}$ at $95\%$ confidence. Our results suggest that resonant neutrino self-interactions are unlikely to resolve existing cosmological tensions within the standard $Λ$CDM framework.

Figures (6)

• Figure 1: Ratio of the linear and nonlinear matter power spectra of RNSI with respect to the $\Lambda$CDM model at $z=0.38$. Each mediator mass $m_{\phi}$ is represented by a different color; the solid line corresponds to the linear comparison, while the dashed line shows the ratio between the real matter power spectra including contributions up to one-loop order. The shaded gray region highlights the scales probed by BOSS. Through this work we adopt $k = 0.20\ h \, \text{Mpc}^{-1}$ as the maximum wavenumber where one-loop perturbation theory is expected to remain reliable. Deviations beyond this scale are not physically meaningful and are shown for illustration only.
• Figure 2: Best fits for the redshift-space galaxy power spectrum monopole (left) and quadrupole (right) on the FS+BBN dataset. We present the RSNI best fit for $m_\phi = 10\,$ eV and compare it to $\Lambda$CDM. The data shown correspond to the NGC at $z_{\rm eff} = 0.38$.
• Figure 3: one-dimensional marginalized posterior distributions of $g_\nu$ for different mediator masses in the FS+BBN (left) and FS+Planck (right) analyses. In the FS+BBN case, the mediator masses $m_\phi = 1, 100\, {\rm eV}$ completely saturate their priors, preventing the detection of neutrino self-interaction signature. Consequently, these values are not reported in the companion Table \ref{['tab:constraints']}, where they are instead indicated by a ‘---’ symbol. In contrast, for FS+Planck, $g_\nu$ is detected for all mediator masses. However, for visualization purposes, we truncate the scale. The corresponding triangle plots are shown in Fig. \ref{['fig:triangulars']}.
• Figure 4: Constraints on $\sigma_8$ derived from the combination of different datasets and mediator masses. The error bars indicate the 68% confidence level, while the markers around the middle represent the mean values. BAO+Planck constraints come from Ref. Venzor:2023aka.
• Figure 5: (left) Comparison of the two-dimensional constraints in the $\sum m_\nu$-$g_\nu$ parameter space from BAO+Planck and FS+Planck. The horizontal dashed lines and shaded regions indicate the minimal masses for the normal hierarchy ($\sum m_\nu > 0.059\, {\rm eV}$) and inverted hierarchy ($\sum m_\nu > 0.10\, {\rm eV}$). (right) Comparison of the one-dimensional marginalized posterior distributions for other cosmological parameters. The results are shown for a mediator with $m_\phi = 10\, {\rm eV}$, though similar trends are observed for other mediator masses.