Limit on the Neutrino Mass from the WMAP Three Year Data

We derive an upper limit on the neutrino mass from the WMAP three-year data alone by employing a deterministic minimisation method based on a grid search in multi-parameter space. Assuming the flat LCDM model with power-law adiabatic perturbations, we find the sum of m_nu < 2.0 eV in agreement with the result of the WMAP team. This result, the limit being nearly the same as that from the WMAP first-year data, means that the fundamental limit on the neutrino mass obtainable from the cosmic microwave background alone is already nearly met, as anticipated from the previous analysis. We also clarify the role of the polarisation data in deriving the limit on the neutrino mass.