Effects of Long-lived 10 MeV Scale Sterile Neutrino on Primordial Elemental Abundances and Effective Neutrino Number

Abstract

The primordial lithium abundance inferred from observations of metal-poor stars is ~3 times smaller than the theoretical value in standard big bang nucleosynthesis (BBN) model. We assume a simple model including a sterile neutrino nu_H with mass of O(10) MeV which decays long after BBN. We then investigate cosmological effects of a sterile neutrino decay. We formulate the injection spectrum of nonthermal photons induced by electrons and positrons generated at the nu_H decay, as a function of the nu_H mass and the photon temperature. We then consistently solve (1) the cosmic thermal history, (2) nonthermal nucleosynthesis induced by the nonthermal photons, (3) the baryon-to-photon ratio eta, and (4) the effective neutrino number N_eff. Amounts of energy injection at the nu_H decay are constrained from limits on primordial D and 7Li abundances, the N_eff value, and the cosmic microwave background energy spectrum. We find that 7Be is photodisintegrated and the Li problem is partially solved for the lifetime 10^4-10^5 s and the mass >~ 14 MeV. 7Be destruction by more than a factor of 3 is not possible because of an associated D over-destruction. In the parameter region, the eta value is decreased slightly, while the N_eff value is increased by a factor of <~ 1. In this study, errors in photodisintegration cross sections of 7Be(g, a)3He and 7Li(g, a)3H that have propagated through literatures are corrected. It is then found that the new photodisintegration rates are 2.3 to 2.5 times smaller than the old rates, so that efficiencies of 7Be and 7Li photodisintegration are significantly smaller.

34 pages, 16 figures, major corrections made, contents extended, Figures corrected and added, conclusion unchanged

References in corpus (15)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Nucleosynthetic signatures of the first stars
• The Primordial Lithium Problem
• Big Bang Nucleosynthesis Constraints on Hadronically and Electromagnetically Decaying Relic Neutral Particles
• How to find neutral leptons of the nuMSM?
• First stars VII. Lithium in extremely metal poor dwarfs
• Atomic Diffusion and Mixing in Old Stars I. VLT/FLAMES-UVES Observations of Stars in NGC 6397
• Evaluation of Modern 3He(alpha,gamma)7Be Data
• Mixing of Active and Sterile Neutrinos
• Activation measurement of the 3He(a,g)7Be reaction cross section at high energies
• Updated constraint on a primordial magnetic field during big bang nucleosynthesis and a formulation of field effects
• ${}^6$Li Production by the Radiative Decay of Long-Lived Particles
• The Cosmological Evolution of the Average Mass Per Baryon
• New Constraints on Radiative Decay of Long-Lived Particles in Big Bang Nucleosynthesis with New ${}^4$He Photodisintegration Data
• Solution to Big-Bang Nucleosynthesis in Hybrid Axion Dark Matter Model

Cited by in corpus (10)

• Constraints on Sterile Neutrinos in the MeV to GeV Mass Range
• Non-universal BBN bounds on electromagnetically decaying particles
• A loophole to the universal photon spectrum in electromagnetic cascades: application to the "cosmological lithium problem"
• The surprising influence of late charged current weak interactions on Big Bang Nucleosynthesis
• Review on Effects of Long-lived Negatively Charged Massive Particles on Big Bang Nucleosynthesis
• Production of heavy sterile neutrinos from vector boson decay at electroweak temperatures
• Impacts of Hawking Radiation from Primordial Black Holes in Critical Collapse Model on the Light Element Abundances
• Cosmological Bounds on sub-GeV Dark Vector Bosons from Electromagnetic Energy Injection
• Updated cosmological constraints on Macroscopic Dark Matter
• Dark matter with excitable levels