Equilibration of the chiral asymmetry due to finite electron mass in electron-positron plasma

We calculate the rate of collisional decay of the axial charge in an ultrarelativistic electron-positron plasma, also known as the chirality flipping rate. We find that contrary to the existing estimates, the chirality flipping rate appears already in the first order in the fine-structure constant α...

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Bibliographic Details
Published in:Physical review. D 2021-01, Vol.103 (1), p.1, Article 013003
Main Authors: Boyarsky, A., Cheianov, V., Ruchayskiy, O., Sobol, O.
Format: Article
Language:English
Subjects:
Chirality
Decay rate
Elastic scattering
Electron mass
Electron-positron plasmas
Electrons
Fermions
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Summary:We calculate the rate of collisional decay of the axial charge in an ultrarelativistic electron-positron plasma, also known as the chirality flipping rate. We find that contrary to the existing estimates, the chirality flipping rate appears already in the first order in the fine-structure constant α and is therefore orders of magnitude greater than previously believed. The main channels for the rapid relaxation of the axial charge are the collinear emission of a weakly damped photon and the Compton scattering. The latter contributes to the O(α) result because of the infrared divergence in its cross section, which is regularized on the soft scale ∼ eT due to the thermal corrections. Our results are important for the description of the early Universe processes (such as leptogenesis or magnetogenesis) that affect differently left- and right-chiral fermions of the Standard Model, as discussed in more details in the companion Letter.
ISSN:2470-0010
2470-0029
DOI:10.1103/PhysRevD.103.013003