Primordial lepton asymmetries in the precision cosmology era: Current status and future sensitivities from BBN and the CMB

• DOI: 10.1103/physrevd.107.035024
• Publication Date: 2023-02-21T15:25:16Z
• Authors: Miguel Escudero; Alejandro Ibarra; Victor Maura
• Keywords: Big Bang nucleosynthesis; Dark radiation; Cosmic background radiation

Using a new sample of extremely metal poor systems, the EMPRESS survey has recently reported primordial helium abundance that is $3\sigma$ smaller than prediction from standard big bang nucleosynthesis (BBN) scenario. This measurement could be interpreted as hint for lepton asymmetry in electron neutrino flavor. Motivated by results, we present comprehensive analysis using measurements abundances elements, along with cosmic microwave background (CMB) data Planck. Assuming there no dark radiation our Universe, find an chemical potential $\xi_{\nu_e} = 0.043 \pm 0.015$, which deviates zero $2.9\sigma$. If assumption made on 0.046 0.021$, $2.2\sigma$. We also this result rather insensitive to choice nuclear reaction rates. true corresponds central value, future CMB observations Simons Observatory and CMB-S4 will increase significance nonzero $4\sigma$ $5\sigma$ respectively, assuming radiation, or when radiation.