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Upper Limit on the QCD Axion Mass from Isolated Neutron Star Cooling
Malte Buschmann1, Christopher Dessert2,3,4, Joshua W Foster5
1Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
Physical Review Letters
|March 18, 2022
Summary
We found no evidence of quantum chromodynamics (QCD) axions affecting neutron star cooling. This study constrains axion mass to below 16 meV, offering insights into particle physics and astrophysics.
Area of Science:
- * Astrophysics and particle physics research.
- * Investigating exotic particles and their cosmic implications.
Background:
- * Neutron stars (NSs) are dense stellar remnants.
- * The quantum chromodynamics (QCD) axion is a hypothetical particle proposed to solve the strong CP problem.
- * Axions may influence NS cooling rates through production mechanisms like nucleon bremsstrahlung and Cooper pair breaking.
Purpose of the Study:
- * To investigate the impact of QCD axions on neutron star cooling.
- * To use nearby isolated neutron stars as targets for axion detection.
- * To constrain the mass of the QCD axion.
Main Methods:
- * Analyzing cooling data from four nearby isolated neutron stars and PSR J0659.
- * Performing dedicated NS cooling simulations incorporating axion emissivity.
- * Profiling uncertainties in equation of state, NS mass, composition, and superfluidity.
- * Calculating axion and neutrino emissivities with high-density suppression factors.
Main Results:
- * No evidence for axion cooling was found in the analyzed neutron star data.
- * The study constrains the QCD axion mass (m_a) to be less than approximately 16 meV at 95% confidence level within the Kim-Shifman-Vainshtein-Zakharov model.
- * High-density suppression factors were included in emissivity calculations, relevant for SN 1987A and previous NS cooling limits.
Conclusions:
- * The current data from isolated neutron stars do not support the presence of QCD axions influencing their cooling.
- * The study provides a significant constraint on the QCD axion mass.
- * Future improvements in understanding NS cooling and nucleon superfluidity could enhance axion detection capabilities or lead to discovery at weaker couplings.
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