2025/05/28 by Banerjee, Arka, Bhattacharjee, Abhik, Das, Subinoy +2 · 2 citations
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2505.22775
In this work, we present Fisher forecasts on non-thermal LiMR models for the upcoming CMB Stage IV experiment -- particularly focusing on a model of inflaton/moduli decay giving rise to non-thermally distributed dark sector particles, and also comparing our results with those for sterile particles following the Dodelson-Widrow distribution. Two independent parameters, the effective number of extra relativistic species ΔNeff and the effective mass Mspeff of the relic, influence linear cosmological observables. We find ΔNeff to be more tightly constrained with σ(ΔNeff)∼10-3, for a less abundant, heavier LiMR which becomes fully non-relativistic around matter-radiation equality than a more abundant, lighter LiMR which becomes fully non-relativistic just after recombination, for which σ(ΔNeff)∼10-2. The uncertainties on Mspeff differ by a factor of ∼3 between the two cases. Our analysis also reveals distinct parameter correlations: the phenomenological parameters \ΔNeff, Mspeff\ are found to be negatively correlated for the former case and positively correlated for the latter. We obtain similar constraints on the cosmological parameters (in either case) for both the inflaton/moduli decay and the Dodelson-Widrow models when the first two moments of the LiMR distribution function, related to the phenomenological parameters, are matched. Finally, by constructing a modified distribution that matches the first two moments of the Dodelson-Widrow but deviates maximally in the third moment, we demonstrate that CMB Stage IV data is not expected to be sensitive to higher moments of the distribution.