Forecast on lepton asymmetry from future CMB experiments

TL;DR

This paper forecasts the potential to measure cosmological lepton asymmetry and neutrino mass scale using future CMB experiments like CORE and CMB-S4, highlighting the possibility of detecting non-zero neutrino degeneracy parameters.

Contribution

It provides updated sensitivity forecasts for lepton asymmetry and neutrino mass scale measurements with upcoming CMB experiments, considering a three-neutrino scenario.

Findings

CORE and CMB-S4 can constrain the degeneracy parameter $\xi_{ u}$ within 0.04 to 0.10 at 95% CL.

Future experiments may detect a non-zero $\xi_{ u}$, impacting the understanding of neutrino physics.

Normal hierarchy is favored in neutrino mass scale evaluations.

Abstract

We consider a cosmological lepton asymmetry in the form of neutrinos and impose new expected sensitivities on such asymmetry through the degeneracy parameter ($\xi_{\nu}$) by using some future CMB experiment configurations, such as CORE and CMB-S4. Taking the default scenario with three neutrino states, we find $\xi_{\mu} = 0.05 \pm 0.10 \, (\pm \, 0.04)$, from CORE (CMB-S4) at 95 percent CL, respectively. Also, within this scenario, we evaluate the neutrino mass scale, obtaining that the normal hierarchy mass scheme is privileged. Our results are an update concerning on the cosmological lepton asymmetry and the neutrino mass scale within this context, from which can bring a perspective on the null hypothesis for $\xi_{\nu}$ (and its effects on $\Delta N_{\rm eff}$), where perhaps, \textbf{$\xi_{\nu}$} may take a non-null value up to 95 percent CL from future experiments such as CMB-S4. Sensitivity results for CMB-S4 obtained here not including all expected systematic errors.