Core Composition Effects on the QCD Axion Mass Limit from Neutron Star Cooling
Abstract
Neutron stars are very dense media in which axions may be produced. This has been used to set a limit on the QCD axion mass, usually under the assumption that only neutrons, protons, electrons, and muons appear in the star core. Given the extreme conditions reached within neutron stars, it is reasonable to consider that other particles, such as hyperons and Δ resonances, may appear in the neutron star core. In this work, we study how the limit on the mass of QCD axions, namely KSVZ and DFSZ invisible axions, is altered when different equations of state are used, allowing for heavier particles to appear in the neutron star core. We find that this dependence is in general mild and thus reinforces the reliability of the known limit. Additionally, in the DFSZ scenario, it may drive the limit within the sensitivity window for IAXO. This would allow this experiment to discern the composition of neutron star cores if an axion were to be observed within that window.
Versions
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BibTeX
@misc{ariasaragon2026core,
title = {{Core Composition Effects on the QCD Axion Mass Limit from Neutron Star Cooling}},
author = {Fernando Arias-Aragón and Federico Nola},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.07742},
eprint = {2606.07742},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.07742},
}
RIS
TY - UNPB
TI - Core Composition Effects on the QCD Axion Mass Limit from Neutron Star Cooling
AU - Fernando Arias-Aragón
AU - Federico Nola
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2606.07742
UR - https://arxiv.org/abs/2606.07742
AB - Neutron stars are very dense media in which axions may be produced. This has been used to set a limit on the QCD axion mass, usually under the assumption that only neutrons, protons, electrons, and muons appear in the star core. Given the extreme conditions reached within neutron stars, it is reasonable to consider that other particles, such as hyperons and Δ resonances, may appear in the neutron star core. In this work, we study how the limit on the mass of QCD axions, namely KSVZ and DFSZ invisible axions, is altered when different equations of state are used, allowing for heavier particles to appear in the neutron star core. We find that this dependence is in general mild and thus reinforces the reliability of the known limit. Additionally, in the DFSZ scenario, it may drive the limit within the sensitivity window for IAXO. This would allow this experiment to discern the composition of neutron star cores if an axion were to be observed within that window.
ER -