Observational constraints on secret neutrino interactions from big bang nucleosynthesis

• Published in: Physical Review D
• Main Authors: Huang, Guo-yuan, Ohlsson, Tommy, Zhou, Shun
• Other Authors: Raunvísindastofnun (HÍ), Science Institute (UI), Verkfræði- og náttúruvísindasvið (HÍ), School of Engineering and Natural Sciences (UI), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Physical Society (APS) 2018
• Subjects: Big bang nucleosynthesis; Neutrino interactions; Neutrinos; Miklihvellur; Heimsfræði; Atóm; Kjarneðlisfræði; Iceland
• Online Access: https://hdl.handle.net/20.500.11815/972; https://doi.org/10.1103/PhysRevD.97.075009

Publisher's version (útgefin grein) We investigate possible interactions between neutrinos and massive scalar bosons via g ϕ ¯ ν ν ϕ (or massive vector bosons via g V ¯ ν γ μ ν V μ ) and explore the allowed parameter space of the coupling constant g ϕ (or g V ) and the scalar (or vector) boson mass m ϕ (or m V ) by requiring that these secret neutrino interactions (SNIs) should not spoil the success of big bang nucleosynthesis (BBN). Incorporating the SNIs into the evolution of the early Universe in the BBN era, we numerically solve the Boltzmann equations and compare the predictions for the abundances of light elements with observations. It turns out that the constraint on g ϕ and m ϕ in the scalar-boson case is rather weak, due to a small number of degrees of freedom (d.o.f.). However, in the vector-boson case, the most stringent bound on the coupling g V ≲ 6 × 10 − 10 at 95% confidence level is obtained for m V ≃ 1 MeV , while the bound becomes much weaker g V ≲ 8 × 10 − 6 for smaller masses m V ≲ 10 − 4 MeV . Moreover, we discuss in some detail how the SNIs affect the cosmological evolution and the abundances of the lightest elements. This work was in part supported by the National Natural Science Foundation of China under Grant No. 11775232, by the National Recruitment Program for Young Professionals and the CAS Center for Excellence in Particle Physics (CCEPP). T. O. acknowledges support by the Swedish Research Council (Vetenskapsrådet) through Contract No. 2017-03934 and the KTH Royal Institute of Technology for a sabbatical period at the University of Iceland. Peer Reviewed