Robust Cosmological Bounds on Neutrinos and their Combination with Oscillation Results

TL;DR

This work investigates how allowing curvature, a dynamic dark energy equation of state, extra relativistic species, and nonzero neutrino masses affects cosmological bounds on the neutrino mass scale. It implements a 10-parameter framework $o\omega{CDM}+\Delta N_{rel}+m_\nu$ and analyzes CMB, $H_0$, SN, and LSS data, comparing the full LSS power spectrum to BAO-only constraints. The authors find degeneracies among $Ω_k$, $ΔN_{rel}$, and $Σ m_ν$ that weaken standard ΛCDM bounds, with $Σ m_ν$ upper limits up to 1.5 eV (BAO) or 0.76 eV (LSSPS), depending on the data combination; they also merge these cosmological bounds with oscillation data to derive projected ranges for $m_{ν_e}$ and $m_{ee}$, some of which are within reach of upcoming experiments such as KATRIN and next-generation $0νββ$ searches. The study demonstrates the importance of multi-probe analyses for robustly constraining the absolute neutrino mass scale in beyond-ΛCDM cosmologies.

Abstract

We perform a global analysis of cosmological observables in generalized cosmologies which depart from $Λ$CDM models by allowing non-vanishing curvature $Ω_k\neq 0$, dark energy with equation of state with $ω\neq -1$, the presence of additional relativistic degrees of freedom $ΔN_{\rm rel}$, and neutrino masses $Ω_ν\neq 0$. By combining the data from cosmic microwave background (CMB) experiments (in particular the latest results from WMAP-7), the present day Hubble constant (H0) measurement, the high-redshift Type-I supernovae (SN) results and the information from large scale structure (LSS) surveys, we determine the parameters in the 10-dimensional parameter space for such models. We present the results from the analysis when the full shape information from the LSS matter power spectrum (LSSPS) is included versus when only the corresponding distance measurement from the baryon acoustic oscillations (BAO) is accounted for. We compare the bounds on the neutrino mass scale in these generalized scenarios with those obtained for the 6+1 parameter analysis in $Λ{\rm CDM}+m_ν$ models and we also study the dependence of those on the set of observables included in the analysis. Finally we combine these results with the information on neutrino mass differences and mixing from the global analysis of neutrino oscillation experiments and derive the presently allowed ranges for the two laboratory probes of the absolute scale of neutrino mass: the effective electron neutrino mass in single beta decay and the effective Majorana neutrino mass in neutrinoless $ββ$ decay.