Bounds on neutrino-scalar nonstandard interactions from big bang nucleosynthesis

Coherent forward scattering processes by neutrino-scalar nonstandard interactions (SNSI) induce an effective neutrino mass. In the early Universe, a large neutrino effective mass restricts the production of neutrinos. The SNSI effect is modulated by two effective couplings; these account for the coupling between neutrinos and electrons or positrons, G(eff), and the neutrino self-interaction G(S). These parameters are directly related to the effective number of relativistic species, and nonzero values imply a smaller than expected N-eff. We employ big bang nucleosynthesis to constraint the SNSI effect. We find that G(eff) < 1.2 MeV-2 and G(S) <2.0 x 10(7) MeV-2 at 68% C.L. For a scalar mass in the range 10(-15 )eV less than or similar to m(phi) less than or similar to 10(-5) eV, our neutrino-scalar coupling constraint is more restrictive than any previous result.

Automated summary

Coherent forward scattering processes by neutrino-scalar nonstandard interactions induce an effective neutrino mass, limiting neutrino production in the early Universe. The effect is modulated by two effective couplings, G(eff) and G(S), which are related to the effective number of relativistic species. Constraints on these parameters are obtained using big bang nucleosynthesis, with implications for the neutrino-scalar coupling.