Gamma ray astrophysics, the extragalactic background light, and new physics

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Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. However, recent observations of cosmologically distant emitters by ground based gamma-ray telescopes might be indicative of a higher-than-expected degree of transparency of the universe. One mechanism to explain this observation is the oscillation between photons and axion-like-particles (ALPs). Here we explore this possibility, focusing on photon-ALP conversion in the magnetic fields in and round gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into ... continued below

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6 pages

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Serpico, Pasquale D. September 1, 2008.

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Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. However, recent observations of cosmologically distant emitters by ground based gamma-ray telescopes might be indicative of a higher-than-expected degree of transparency of the universe. One mechanism to explain this observation is the oscillation between photons and axion-like-particles (ALPs). Here we explore this possibility, focusing on photon-ALP conversion in the magnetic fields in and round gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into photons. We show that this mechanism can be efficient in allowed regions of the ALP parameter space, as well as in typical configurations of the Galactic Magnetic Field. As case example, we consider the spectrum observed from a HESS source. We also discuss features of this scenario which could be used to distinguish it from standard or other exotic models.

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6 pages

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  • Presented at 37th COSPAR Scientific Assembly and Associated Events, Montreal, Canada, 13-20 Jul 2008

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  • Report No.: FERMILAB-CONF-08-291-A
  • Grant Number: AC02-07CH11359
  • Office of Scientific & Technical Information Report Number: 938459
  • Archival Resource Key: ark:/67531/metadc893413

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • September 1, 2008

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  • Sept. 27, 2016, 1:39 a.m.

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  • Sept. 26, 2017, 12:23 p.m.

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Serpico, Pasquale D. Gamma ray astrophysics, the extragalactic background light, and new physics, article, September 1, 2008; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc893413/: accessed December 10, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.