Determination of neutrino mass hierarchy by 21 cm line and CMB B-mode polarization observations

TL;DR

This paper investigates how future 21 cm line and CMB B-mode polarization observations can determine the neutrino mass hierarchy and improve bounds on neutrino properties.

Contribution

It demonstrates that combining specific observational data sets can distinguish the neutrino mass hierarchy and tighten constraints on neutrino mass and species.

Findings

CMB + 21 cm observations can determine neutrino mass hierarchy at 2 sigma.

Planck + POLARBEAR + SKA can reduce errors on neutrino mass to ~0.12 eV.

Combination of observations improves bounds on effective neutrino number.

Abstract

We focus on the ongoing and future observations for both the 21 cm line and the CMB B-mode polarization produced by a CMB lensing, and study their sensitivities to the effective number of neutrino species, the total neutrino mass, and the neutrino mass hierarchy. We find that combining the CMB observations with future square kilometer arrays optimized for 21 cm line such as Omniscope can determine the neutrino mass hierarchy at 2 sigma. We also show that a more feasible combination of Planck + POLARBEAR and SKA can strongly improve errors of the bounds on the total neutrino mass and the effective number of neutrino species to be Delta Sigma m_nu ~ 0.12 eV and Delta N_nu ~ 0.38 at 2 sigma.