Updated Bounds on Sum of Neutrino Masses in Various Cosmological Scenarios

TL;DR

This paper derives stringent upper bounds on the sum of neutrino masses using various cosmological datasets and models, approaching the minimum mass required for inverted hierarchy, with bounds tightening under different assumptions.

Contribution

It provides updated, tighter bounds on neutrino masses across multiple cosmological models using comprehensive datasets and explores the impact of different parameters and priors.

Findings

Upper bound of 0.118 eV with Planck polarization data

Further reduced to 0.093 eV with combined datasets and models

Bounds are sensitive to assumptions about dark energy and Hubble constant

Abstract

We present strong bounds on the sum of three active neutrino masses ($\sum m_{\nu}$) in various cosmological models. We use the following baseline datasets: CMB temperature data from Planck 2015, BAO measurements from SDSS-III BOSS DR12, the newly released SNe Ia dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters in $\Lambda CDM$ model with 3 massive active neutrinos. For this $\Lambda CDM+\sum m_{\nu}$ model we find a upper bound of $\sum m_{\nu} <$ 0.152 eV at 95$\%$ C.L. Adding the high-$l$ polarization data from Planck strengthens this bound to $\sum m_{\nu} <$ 0.118 eV, which is very close to the minimum required mass of $\sum m_{\nu} \simeq$ 0.1 eV for inverted hierarchy. This bound is reduced to $\sum m_{\nu} <$ 0.110 eV when we also vary r, the tensor to scalar ratio ($\Lambda CDM+r+\sum m_{\nu}$ model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration. This bound is further reduced to $\sum m_{\nu} <$ 0.101 eV in a cosmology with non-phantom dynamical dark energy ($w_0 w_a CDM+\sum m_{\nu}$ model with $w(z)\geq -1$ for all $z$). Considering the $w_0 w_a CDM+r+\sum m_{\nu}$ model and adding the BK14 data again, the bound can be even further reduced to $\sum m_{\nu} <$ 0.093 eV. For the $w_0 w_a CDM+\sum m_{\nu}$ model without any constraint on $w(z)$, the bounds however relax to $\sum m_{\nu} <$ 0.276 eV. Adding a prior on the Hubble constant ($H_0 = 73.24\pm 1.74$ km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to $\sum m_{\nu} <$ 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3$\sigma$ tension between Planck 2015 and HST measurements of $H_0$ and should be taken cautiously. (abstract abridged)