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Unstable massive tau-neutrinos and primordial nucleosynthesis

A. D. Dolgov·S. H. Hansen·S. Pastor·D. V. Semikoz
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Abstract

The impact of unstable Majorana tau neutrinos on primordial nucleosynthesis is considered. The mass and lifetime of nu_tau are taken in the intervals 0.1-20 MeV and 0.001-400 sec respectively. The studied decay modes are nu_tau -> nu_mu + phi and nu_tau -> nu_e + phi, where phi is a massless (or light) scalar. Integro-differential kinetic equations are solved numerically without any simplifying assumptions. Our results deviate rather strongly from earlier calculations. Depending on mass, lifetime, and decay channels of the nu_tau, the number of effective neutrino species (found from He4), in addition to the 3 standard ones, varies from -2 to +2.5. The abundances of H2 and Li7 are also calculated.

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A. D. Dolgov, S. H. Hansen, S. Pastor, D. V. Semikoz. 1999-02-28. Unstable massive tau-neutrinos and primordial nucleosynthesis. https://doi.org/10.1016/s0550-3213(99)00127-3

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