Study Examines How Neutron Star Core Composition Affects QCD Axion Mass Constraints
Researchers investigated how different particle compositions in neutron star cores influence limits on the mass of QCD axions, a hypothetical dark matter candidate. The study considered scenarios where heavier particles like hyperons and Delta resonances exist alongside standard neutrons and protons, rather than assuming only lighter particles. The findings suggest that while composition effects are generally modest, they could potentially bring certain axion models within the detection range of the IAXO experiment.
A new theoretical study from arXiv examines how the internal composition of neutron stars affects constraints on QCD axion mass derived from stellar cooling observations. Neutron stars are extremely dense objects where axions could be produced, allowing astronomers to set upper limits on axion mass by observing how quickly these stars cool. Previous analyses typically assumed neutron star cores contain only neutrons, protons, electrons, and muons. This work explores how allowing heavier particles—such as hyperons and Delta resonances—to exist in the core under extreme conditions alters these mass limits for both KSVZ and DFSZ axion models. The researchers find that composition-dependent variations in the mass limits are generally mild, supporting the robustness of existing constraints. Notably, for the DFSZ scenario, these effects could shift the predicted axion mass into the sensitivity range of the IAXO (International Axion Observatory) experiment, potentially enabling future observations to constrain neutron star core composition.
What's missing
The study does not discuss the current experimental status of axion detection efforts beyond mentioning IAXO's sensitivity window, nor does it address how the proposed mechanism compares quantitatively to other astrophysical axion constraints (e.g., from supernovae or white dwarfs). The specific numerical values of the mass limits under different equations of state are not provided in the abstract.
What different sources said
- arXiv astro-phCenter
On the effect of higher order symmetry energy corrections in Skyrme models for neutron star matter
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