Constraints from nucleosynthesis and SN 1987A on Majoron-emitting double beta decay.

We examine whether observable majoron emission in double beta decay can be compatible with the big-bang nucleosynthesis (NS) and the observed neutrino flux from SN1987A. It is found that the NS upper bound on 4 He abundance implies that the majoron-neutrino Yukawa coupling constant g ≤ 9 × 10 6 and its maximal value is allowed only when the scalar quartic coupling constant λ is extremely small, λ ≤ 100g 2 . It is also observed that, although quite less restrictive, SN1987A also provides independent constraints on coupling constants.