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arXiv · 2211.05073

Axion-pion thermalization rate in unitarized NLO chiral perturbation theory

Luca Di Luzio·Jorge Martin Camalich·Guido Martinelli·José Antonio Oller·Gioacchino Piazza
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Abstract

We compute the axion-pion scattering $a \pi \to \pi \pi$, relevant for the axion thermalization rate in the early universe, within unitarized NLO chiral perturbation theory. The latter extends the range of validity of the chiral expansion of axion-pion scattering and thus provides a crucial ingredient for the reliable determination of the relic density of thermal axions, whenever the axion decoupling temperature is below that of the QCD phase transition. Implications for cosmological observables are briefly discussed.

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Luca Di Luzio, Jorge Martin Camalich, Guido Martinelli, José Antonio Oller, Gioacchino Piazza. 2022-11-09. Axion-pion thermalization rate in unitarized NLO chiral perturbation theory. https://doi.org/10.1103/physrevd.108.035025

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