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

1 Aug 2020  ·  A. Boyarsky, V. Cheianov, O. Ruchayskiy, O. Sobol ·

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. read more

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High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics High Energy Physics - Theory