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Astrophysical effects of axions and axion-like particles

by Prof. Marco Roncadelli (INFN & University of Pavia)

Mar 16, 2015 from 02:30 PM to 04:00 PM

Where IRA meeting room (4th floor, CNR research area, via Gobetti 101)

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Axions and axion-like particles (ALPs) are predicted by several extensions of the Standard Model and especially by those involving compactified extra-dimensions such as superstring theories. While both couple to two-photons, axions also couple to matter. In either case, they are good candidates for cold dark matter and can cause an efficient energy-loss channel for stars of various kinds. ALPs can give rise to observable effects in the very-high-energy (VHE) band (100 GeV -- 100 TeV), which is currently probed by the Imaging Atmospheric Cherenkov Telescopes H.E.S.S., MAGIC and VERITAS, and in the future by the CTA (Cherenkov Telescope Array). Blazar observations provide three independent hints of the existence of an ALP, since it explains three unexpected effects: the lower-than-predicted opacity of the Universe in the VHE band, the VHE emission of flat spectrum radio quasars and the unphysical redshift-dependence of the VHE emitted blazar spectra. An ALP with the required properties can be detected in the near future by the laboratory experiment ALPS at DESY.

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