What question did this study set out to answer?

This research aims to determine the scales at which chiral perturbation theory (χPT) breaks down for the axial-vector coupling constant gA and the nucleon mass mN.

April 25, 2026Open Access

Inferring the Breakdown Scales of the Chiral Expansions for gA and mN

Key Points

This research aims to determine the scales at which chiral perturbation theory (χPT) breaks down for the axial-vector coupling constant gA and the nucleon mass mN.
Applied Bayesian inference to chiral perturbation theory expansions for gA and mN.
Conducted pointwise Bayesian analysis using two distinct sets of low-energy constants.
Inferred breakdown scale for gA as 251+20−50 MeV and 211+20−30 MeV for different low-energy constants.
Inferred breakdown scale for mN as 491+60−90 MeV, indicating it is significantly larger than for gA.

Abstract

We apply Bayesian inference to the order-by-order chiral perturbation theory (χPT) expansions for the axial-vector coupling constant gA and the nucleon mass mN, and thereby infer the scales at which χPT breaks down for these two observables. Using a pointwise Bayesian analysis, we find that the inferred breakdown scales are notably different for the two observables. For the chiral expansion of gA, we obtain 251+20−50 MeV and 211+20−30 MeV using two distinct sets of low-energy constants, while for the chiral expansion of mN we infer a significantly larger breakdown scale of 491+60−90 MeV.

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Ekström et al. (Wed,) studied this question.

synapsesocial.com/papers/69ec5b3d88ba6daa22daccbf https://doi.org/https://doi.org/10.1016/j.physletb.2026.140352">https://doi.org/10.1016/j.physletb.2026.140352</a></p

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