The primordial helium abundance and the number of neutrino families

Peimbert, A. (1), Peimbert, M. (1), and Luridiana, V. (2,3)

(1) Instituto de Astronomía, Universidad Nacional Autónoma de México, México.
(2) Instituto de Astrofísica de Canarias, Spain. (3) Departamento de Astrofísica, Universidad de La Laguna, Spain.

Based on observations of H II regions and the new computations of the recombination coefficients of the He I lines by Porter et al. (2013) we obtain a primordial helium abundance by mass of Yp =0.2446±0.0029. We consider thirteen sources of error for the Yp determination, some of them are mainly due to systematic effects, while the rest are mainly due to statistical effects. We compare our results with other determinations of Yp   present in the literature. Combining our Yp value with computations of primordial nucleosynthesis we find a number of neutrino species Neff =2.90±0.22, and a neutron mean life τν = 872 ± 14 (s).

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