Heavy axionlike particles (ALPs) with masses up to a few 100 keV and coupled with photons can be efficiently produced in stellar plasmas. We present a new “ballistic” recipe that covers both the energy-loss and energy-transfer regimes, and we perform the first dedicated simulation of Globular Cluster stars including the ALP energy transfer. This argument allows us to constrain ALPs with $m_a\lesssim 0.4\mathrm{MeV}$ and $g_{a\gamma }\simeq {10}^{-5}{\mathrm{GeV}}^{-1}$, probing a section of the ALP parameter space informally known as the “cosmological triangle”. This region is particularly interesting since it has been excluded only using standard cosmological arguments that can be evaded in nonstandard scenarios.

• Received 12 March 2022
• Revised 4 May 2022
• Accepted 13 June 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.011101

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society