Volume 119, Number 2, July 2017
|Number of page(s)||6|
|Section||Geophysics, Astronomy and Astrophysics|
|Published online||29 September 2017|
Improved constraints on lepton asymmetry from the cosmic microwave background
Fakultät für Physik, Bielefeld University - D-33501 Bielefeld, Germany
Received: 21 June 2017
Accepted: 5 September 2017
A cosmic lepton asymmetry affects the primordial helium abundance and the expansion rate of the early Universe. Both of these effects have an impact on the anisotropies of the cosmic microwave background (CMB). We derive constraints on the neutrino chemical potentials from the Planck 2015 data, assuming equal lepton flavour asymmetries and negligible neutrino masses. We find (95% CL) for the chemical potentials, which corresponds to . Our constraints on the lepton asymmetry are significantly stronger than previous constraints from CMB data analysis and we argue that they are more robust than those from primordial light element abundances. The resulting constraints on the primordial helium and deuterium abundances are consistent with those from direct measurements.
PACS: 98.80.-k – Cosmology / 98.70.Vc – Background radiations / 26.35.+c – Big Bang nucleosynthesis
© EPLA, 2017
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