CERN Accelerating science

Article
Report number	arXiv:2208.03237 ; CERN-TH-2022-134 ; RESCEU-13/22 ; KEK-TH-2441 ; MS-TP-22-23 ; TU-1164
Title	New Constraint on Primordial Lepton Flavor Asymmetries
Author(s)	Domcke, Valerie (CERN ; EPFL, Lausanne, LPPC) ; Kamada, Kohei (Tokyo U., RESCEU) ; Mukaida, Kyohei (KEK, Tsukuba ; Sokendai, Tsukuba) ; Schmitz, Kai (Munster U.) ; Yamada, Masaki (Tohoku U., Astron. Inst. ; Tohoku U.)
Publication	2023-06-30
Imprint	2022-08-05
Number of pages	7
In:	Phys. Rev. Lett. 130 (2023) 261803
DOI	10.1103/PhysRevLett.130.261803 (publication)
Subject category	astro-ph.CO ; Astrophysics and Astronomy ; hep-ph ; Particle Physics - Phenomenology
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.
Copyright/License	preprint: (License: CC BY 4.0) publication: © 2023-2025 authors (License: CC BY 4.0), sponsored by SCOAP³

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