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Primodal nucleosynthesis, additional neutrinos and neutral currents from the superstring

1986; Elsevier BV; Volume: 167; Issue: 4 Linguagem: Inglês

10.1016/0370-2693(86)91301-8

1873-2445

John Ellis, Kari Enqvist, D.V. Nanopoulos, S. Sarkar,

Dark Matter and Cosmic Phenomena

The constraint on the number of neutrino species Nv imposed by Big Bang nucleosynthesis is reviewed critically. It is argued that uncertainites in the neutron lifetime, systematic errors in the measurement of 4He abundance, and new astrophysical data on 3He which suggest extensive astration of D, permit Nv = 5 or even 6. Some phenomenological models based on the superstring expect three additional right-handed neutrinos of low mass which are weakly coupled to ordinary matter through a new heavy Z′ gauge boson. Their compatibility with the relaxed nucleosynthesis limits quoted above imposes an interesting lower limit on mZ′. As a byproduct of our analysis, we present the corrections to low energy vμe scattering due to Z′ exchange.