Constraints on neutrino masses from WMAP5 and BBN in the lepton asymmetric universe

TL;DR

This study uses WMAP5 data and BBN to constrain neutrino masses and lepton asymmetry, finding that neutrino mass limits are robust against lepton asymmetry variations.

Contribution

It introduces a consistent method to incorporate lepton asymmetry effects into neutrino mass constraints using MCMC and BBN calculations.

Findings

Neutrino mass sum constrained to < 1.3 eV at 95% CL.

Constraints remain stable despite allowing lepton asymmetry.

Method improves accuracy of cosmological neutrino property estimates.

Abstract

In this paper, we put constraints on neutrino properties such as mass $m_{\nu}$ and degeneracy parameters $\xi_i$ from WMAP5 data and light element abundances by using a Markov chain Monte Carlo (MCMC) approach. In order to take consistently into account the effects of the degeneracy parameters, we run the Big Bang Nucleosynthesis code for each value of $\xi_i$ and the other cosmological parameters to estimate the Helium abundance, which is then used to calculate CMB anisotropy spectra instead of treating it as a free parameter. We find that the constraint on $m_{\nu}$ is fairly robust and does not vary very much even if the lepton asymmetry is allowed, and is given by $\sum m_\nu < 1.3 \rm eV$ ($95 % \rm C.L.$).