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arXiv · 2310.08169

The QCD Axion: Some Like It Hot

Federico Bianchini·Giovanni Grilli di Cortona·Mauro Valli
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Abstract

We compare the QCD axion phase-space distribution from unitarized next-to-leading order chiral perturbation theory with the one extracted from pion-scattering data. We derive a robust bound by confronting momentum-dependent Boltzmann equations against up-to-date observations of the Cosmic Microwave Background, of the Baryonic Acoustic Oscillations and of primordial abundances. These datasets imply $m_{a} \leq \, 0.16 $ eV for the 95% credible interval, i.e. $\sim$30% stronger bound than what previously found. We present forecasts using dedicated likelihoods for future cosmological surveys and the sphaleron rate from unquenched lattice QCD.

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Federico Bianchini, Giovanni Grilli di Cortona, Mauro Valli. 2023-10-12. The QCD Axion: Some Like It Hot. https://doi.org/10.1103/physrevd.110.123527

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