Cosmological Preference for a Positive Neutrino Mass at 2.7$\sigma$: A Joint Analysis of DESI DR2, DESY5, and DESY1 Data

TL;DR

This study combines multiple cosmological data sets to measure neutrino mass, finding evidence for a positive neutrino mass at 2.7 sigma within a dynamical dark energy model, suggesting neutrinos are more massive than previously confirmed.

Contribution

It provides the first high-confidence measurement of neutrino mass within a dynamical dark energy framework using joint DESI, CMB, supernova, and weak lensing data.

Findings

Neutrino mass measured at 0.098 eV with 2.7 sigma confidence.

Preference for dynamical dark energy with evolving equation of state.

Including free N_eff and weak lensing data increases neutrino mass constraints.

Abstract

Neutrinos and dark energy (DE) have entered a new era of investigation, as the latest DESI baryon acoustic oscillation measurements tighten the constraints on the neutrino mass and suggest that DE may be dynamical rather than a cosmological constant. {In this work, we obtain a high-confidence measurement of the neutrino mass within a dynamical DE framework. A joint analysis of DESI DR2, cosmic microwave background, DESY5 supernova, and DESY1 weak lensing data yields a total neutrino mass of $\sum m_\nu = 0.098^{+0.016}_{-0.037}\,\mathrm{eV}$, indicating a measurement for a non-zero, positive neutrino mass at the $2.7\sigma$ level within the $w_0w_a$CDM framework. This high-confidence measurement is driven mainly by these factors: (i) the DESI's preference for a dynamical DE with its equation of state evolving from $w< -1$ at early times to $w> -1$ at late times, thus leading to a larger neutrino mass; (ii) treating $N_{\mathrm{eff}}$ as a free parameter together with the inclusion of weak lensing data, which likewise allows for an increased neutrino mass.} In future, even higher-confidence measurements of neutrino mass are expected with stronger preferences for dynamical DE in light of more complete DESI data releases.