Equilibration of the chiral asymmetry due to finite electron mass in electron-positron plasma. (arXiv:2008.00360v2 [hep-ph] UPDATED)

Equilibration of the chiral asymmetry due to finite electron mass in electron-positron plasma. (arXiv:2008.00360v2 [hep-ph] UPDATED)
<a href="http://arxiv.org/find/hep-ph/1/au:+Boyarsky_A/0/1/0/all/0/1">A. Boyarsky</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Cheianov_V/0/1/0/all/0/1">V. Cheianov</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Ruchayskiy_O/0/1/0/all/0/1">O. Ruchayskiy</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Sobol_O/0/1/0/all/0/1">O. Sobol</a>

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
$alpha$ 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 $mathcal{O}(alpha)$ result because of the infrared
divergence in its cross section, which is regularized on the soft scale $sim
eT$ 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.

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
$alpha$ 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 $mathcal{O}(alpha)$ result because of the infrared
divergence in its cross section, which is regularized on the soft scale $sim
eT$ 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.

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