Speaker
Description
The effective number of neutrinos, $N_{\mathrm{eff}}$, is an important parameter in standard hot big bang cosmology. In this work, we compute the dominant QED correction to the neutrino-electron interaction rate in the vicinity of neutrino decoupling in the early universe, and estimate its impact on $N_{\mathrm{eff}}$. We find that the correction to the interaction rate is at the sub-percent level. The fractional change in $N_{\mathrm{eff}}$ due to the rate correction is of order or below $10^{-5}$, i.e., about a factor of 30 smaller than that recently claimed by Cielo et al., and below the nominal computational uncertainties of the current benchmark value of $N_{\mathrm{eff}} = 3.0440 ± 0.0002$. We therefore conclude that aforementioned number remains to be the state-of-the-art benchmark for $N_{\mathrm{eff}}$ in the standard model of particle physics.
Based on arXiv:2402.18481
