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

Abstract

In this paper, we put constraints on neutrino properties such as mass $m_ν$ and degeneracy parameters $ξ_i$ 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 $ξ_i$ 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 $m_ν$ is fairly robust and does not vary very much even if the lepton asymmetry is allowed, and is given by $\sum m_ν< 1.3 \rm eV$ ($95 % \rm C.L.$).

19 pages, 7 figures, 5 tables