Average and recommended half-life values for two neutrino double beta decay: upgrade'05

All existing ``positive’’ results on two neutrino double beta decay in different nuclei were analyzed. Using the procedure recommended by the Particle Data Group, weighted average values for half-lives of ${}^{48}$Ca, ${}^{76}$Ge, ${}^{82}$Se, ${}^{96}$Zr, ${}^{100}$Mo, ${}^{100}$Mo - ${}^{100}$Ru ($0_1^{+}$), ${}^{116}$Cd, ${}^{150}$Nd, ${}^{150}$Nd - ${}^{150}$Sm ($0_1^{+}$) and ${}^{238}$U were obtained. Existing geochemical data were analyzed and recommended values for half-lives of ${}^{128}$Te, ${}^{130}$Te and ${}^{130}$Ba are proposed. We recommend the use of these results as presently the most precise and reliable values for half-lives.