The contribution of light Majorana neutrinos to neutrinoless double beta decay and cosmology

Cosmology is making impressive progress and it is producing stringent bounds on the sum of the neutrino masses Sigma, a parameter of great importance for the current laboratory experiments. In this letter, we exploit the potential relevance of the analysis of Palanque-Delabrouille et al. [JCAP 02 (2015) 045] to the neutrinoless double beta decay (0 nu beta beta) search. This analysis indicates small values for the lightest neutrino mass, since the authors find Sigma < 84 meV at 1 sigma C.L., and provides a 1 sigma preference for the normal hierarchy. The allowed values for the Majorana effective mass, probed by 0 nu beta beta, turn out to be < 75 meV at 3 sigma C.L. and lower down to less than 20 meV at 1 sigma C.L.. If this indication is confirmed, the impact on the 0 nu beta beta experiments will be tremendous since the possibility of detecting a signal will be out of the reach of the next generation of experiments.