Axion Physics

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  1. Oindrila Ghosh, Sunniva Jacobsen, Tim Linden
  2. 2501.08978

GRB Observations Strongly Constrain Heavy Axions

Heavy Axions can be very efficiently produced in extremely high temperature plasmas. One of the highest temperature plasmas in the universe is produced in the very early stages of GRB fireballs. These fireballs can form on distance scales of less than 10 km, and achieve temperatures as high as 100 MeV. Once produced, these axions can free-stream outside of the GRB acceleration region, and decay back to photons farther from the main GRB jet. This prevents them from being accelerated up to high energies, and disrupts the production of the high-energy beam that typifies blazar jets. Using observations that high-energy jets have been observed from many GRBs, we strongly constrain the axion parameter space, producing world leading limits on axions with GeV-scale masses.

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  1. Sunniva Jacobsen, Tim Linden, Katherine Freese
  2. 2203.04332
Constraining Axion-Like Particles with HAWC Observations of TeV Blazars

Very high-energy gamma-rays from distant sources are typically attenuated (absorbed and re-emitted at lower energies) through interactions with the extragalactic background light during their intergalactic propagation. This means that while distant blazars are bright at GeV energies, their emission at TeV energies should be highly suppressed. Interactions with axion-like particles can provide an alterative life for these particles, as TeV photons could convert into axions within blazar magnetic fields, and then propagate effectively through the IGM before reconverting into TeV gamma rays in the Milky Way magnetic field. We search TeV gamma-ray emission from bright blazars using the 3HWC catalog in concert with lower-energy telescopes. We find no evidence for a signal consistent with ALPs, and place constraints on the axion-photon coupling that is consistent with, or slightly stronger than previous limits.

  1. Joshua Foster, Samuel Witte, Matthew Lawson, Tim Linden, Vishal Gajjar, Christoph Weniger, Ben Safdi
  2. 2202.08274
Extraterrestrial Axion Search with the Breakthrough Listen Galactic Center Survey

The extremely strong magnetic fields of neutron stars potentially provide an optimal environment to initiate the conversion of dark matter axions into photon signals. The galactic center remains an exciting target for these searches, because previous studies indicate that it has both a large dark matter and neutron star density. We utilize detailed sureys the galactic center produced by the Breakthrough Listen Project, which are directly targeted at finding evidence of extraterrestrial life in our universe. The high energy resolution of these surveys is optimal for the detection of an axion signal. We find no evidence for a radio line produced by axion-photon conversion, and set strong limits on the axion-photon conversion cross-section, the exact strength of which depends on uncertainties in the underlying neutron star and dark matter population -- uncertainties which can be significantly reduced by upcoming experiments over the next decade.

Full Publication List:

3. Heavy Axions Can Disrupt Gamma-Ray Bursts
 Oindrila Ghosh, Sunniva Jacobsen, Tim Linden
To Be Submitted

2. Constraining Axion-Like Particles with HAWC Observations of TeV Blazars
 Sunniva Jacobsen, Tim Linden, Katherine Freese
Journal of Cosmology and Astroparticle Physics 10 009

1. Extraterrestrial Axion Search with the Breakthrough Listen Galactic Center Survey
 Joshua Foster, Samuel Witte, Matthew Lawson, Tim Linden, Vishal Gajjar, Christoph Weniger, Ben Safdi
Physial Review Letters 129, 251102 (2022)

Tim Linden

Assistant Professor, Stockholm University

linden@fysik.su.se