BBN with Late Electron-Sterile Neutrino Oscillations - The Finest Leptometer

TL;DR

This paper presents a BBN model with late electron-sterile neutrino oscillations that can detect extremely small relic lepton asymmetries, significantly improving sensitivity to primordial lepton asymmetry through its impact on helium production.

Contribution

It introduces a fine leptometer based on neutrino oscillations capable of sensing lepton asymmetries as small as 10^{-8}, surpassing previous constraints.

Findings

Sensitive to lepton asymmetry > 10^{-8}

Analyzed influence of L on nucleon freeze-out

Discussed asymmetry generation by oscillations

Abstract

A relic lepton asymmetry orders of magnitude bigger than the baryon one may hide in the relic neutrino background. No direct theoretical or experimental limitations on its magnitude and sign are known. Indirect cosmological constraints exist ranging from $|L|<0.01$ to $L<10$. We discuss a BBN model with late electron-sterile neutrino oscillations which is a fine leptometer - it is capable of feeling extremely small relic lepton asymmetry - $|L|>10^{-8}$. This sensitivity is achieved through the influence of such small $L$ on the neutrino oscillations, suppressing or enhancing them, and thus changing the primordially produced $^4He$. The influence of $L$ on nucleons freezing in pre-BBN epoch is numerically analyzed in the full range of the oscillation parameters of the model and for $ L \ge 10^{-10}$. The case of oscillations generated asymmetry by late electron-sterile oscillations and its effect on primordial $^4He$ is also briefly discussed.