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arXiv · 2208.03237

A new constraint on primordial lepton flavour asymmetries

Valerie Domcke·Kohei Kamada·Kyohei Mukaida·Kai Schmitz·Masaki Yamada
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Abstract

A chiral chemical potential present in the early universe can source helical hypermagnetic fields through the chiral plasma instability. If these hypermagnetic fields survive until the electroweak phase transition, they source a contribution to the baryon asymmetry of the universe. In this letter, we demonstrate that lepton flavour asymmetries above $|\mu|/T \sim 9 \times 10^{-3}$ trigger this mechanism even for vanishing total lepton number. This excludes the possibility of such large lepton flavour asymmetries present at temperatures above $10^6$ GeV, setting a constraint which is about two orders of magnitude stronger than the current CMB and BBN limits.

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Valerie Domcke, Kohei Kamada, Kyohei Mukaida, Kai Schmitz, Masaki Yamada. 2022-08-05. A new constraint on primordial lepton flavour asymmetries. https://doi.org/10.1103/physrevlett.130.261803

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