Revisiting the bound on axion-photon coupling from Globular Clusters

Abstract

We derive a strong bound on the axion-photon coupling $g_{a\gamma }$ from the analysis of a sample of 39 Galactic Globular Clusters. As recognized long ago, the R parameter, i.e. the number ratio of stars in horizontal over red giant branch of old stellar clusters, would be reduced by the axion production from photon conversions occurring in stellar cores. In this regard we have compared the measured R with state-of-the-art stellar models obtained under different assumptions for $g_{a\gamma }$. We show that the estimated value of $g_{a\gamma }$ substantially depends on the adopted He mass fraction Y, an effect often neglected in previous investigations. Taking as benchmark for our study the most recent determinations of the He abundance in H II regions with O/H in the same range of the Galactic Globular Clusters, we obtain an upper bound $g_{a\gamma }<0.66\times 10^{-10}$ GeV${}^{-1}$ at 95$\%$ confidence level. This result significantly improves the constraints from previous analyses and is currently the strongest limit on the axion-photon coupling in a wide mass range.

(v2: 6 pages, 1 eps figure. Revised version. Discussion enlarged and references added. To appear on Physical Review Letters.)

References in corpus (10)

• Bose-Einstein Condensation of Dark Matter Axions
• Evidence for a new light spin-zero boson from cosmological gamma-ray propagation?
• Probing eV-scale axions with CAST
• A High Resolution Search for Dark-Matter Axions
• Axions and the cooling of white dwarf stars
• First measurement of the 14N(p,gamma)15O cross section down to 70 keV
• Constraining the Axion-Photon Coupling with Massive Stars
• Heavy elements in Globular Clusters: the role of AGB stars
• A Method to Derive the Absolute Composition of the Sun, the Solar System and the Stars
• Axion cold dark matter: status after Planck and BICEP2

Cited by in corpus (18)

• Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles
• Stellar cooling bounds on new light particles: plasma mixing effects
• The photo-philic QCD axion
• The Fermi Large Area Telescope as a Galactic Supernovae Axionscope
• Photons to axion-like particles conversion in Active Galactic Nuclei
• Sensitivity of the Cherenkov Telescope Array to the detection of axion-like particles at high gamma-ray opacities
• Towards a medium-scale axion helioscope and haloscope
• A class of invisible axion models with FCNCs at tree level
• Constraining axionlike particles using the distance-duality relation
• Effects of axions on Population III stars
• The Darkness of Spin-0 Dark Radiation
• Non-thermal Axion Dark Radiation and Constraints
• No axions from the Sun
• Theoretical Calculation of coherent Laue-case conversion between X rays and ALPs for an X-ray LSW experiment
• Hints of new physics from stars
• Fermi-LAT and NuSTAR as Stellar Axionscopes
• Modified Supersymmetric Dark Sectors
• Light-shining-through-walls with lasers