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Breaking Be: a sterile neutrino solution to the cosmological lithium problem | | Laura Salvati
; Luca Pagano
; Massimiliano Lattanzi
; Martina Gerbino
; Alessandro Melchiorri
; | | Date: |
22 Jun 2016 | | Abstract: | The possibility that the so-called "lithium problem", i.e., the disagreement
between the theoretical abundance predicted for primordial $^7 ext{Li}$
assuming standard nucleosynthesis and the value inferred from astrophysical
measurements, can be solved through a non-thermal Big Bang Nucleosynthesis
(BBN) mechanism has been investigated by several authors. In particular, it has
been shown that the decay of a MeV-mass particle, like, e.g., a sterile
neutrino, decaying after BBN not only solves the lithium problem, but also
satisfies cosmological and laboratory bounds, making such a scenario worth to
be investigated in further detail. In this paper, we constrain the parameters
of the model with the combination of current data, including Planck 2015
measurements of temperature and polarization anisotropies of the Cosmic
Microwave Background (CMB), FIRAS limits on CMB spectral distortions,
astrophysical measurements of primordial abundances and laboratory constraints.
We find that a sterile neutrino with mass $M_S = 4.35 _{-0.17} ^{+0.13} ,
ext{MeV}$ (at $95\%$ c.l.) and decay time $ au _S = 1.8 _{-1.6} ^{+1.9}
cdot 10^5 , ext{s}$ (at $95\%$ c.l.) perfectly accounts for the difference
between predicted and observed $^7 ext{Li}$ primordial abundance. The same
model also predicts an increase of the effective number of relativistic degrees
of freedom at the time of CMB decoupling $Delta N_ ext{eff}^ ext{cmb}equiv
N_ ext{eff}^ ext{cmb} -3.046 = 0.34 _{-0.14} ^{+0.16}$ at $95\%$ c.l.. We
also provide forecasts for future experiments finding that the combination of
measurements from the COrE+ and PIXIE missions will allow to significantly
reduce the permitted region for the sterile lifetime and density. | | Source: | arXiv, 1606.6968 | | Services: | Forum | Review | PDF | Favorites | |
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