Axion-like particles: hints and constraints from the high-energy universe
Wed, May. 14th 2014, 14:15-15:15
Salle Claude Itzykson, Bât. 774, Orme des Merisiers
Axions and more generically axion-like particles (ALPs) are new particles predicted in extensions of the standard model. They are expected to have a two-photon vertex with a weak coupling strength, and a very small mass, well below the electron-volt level. Axions and ALPs are of prime importance in cosmology and astrophysics, as they could form the cold dark matter and affect the evolution of stellar objects, or even be related to the late-time acceleration of expansion. High-energy astronomy, from X rays to gamma rays, opens a window to search for ALPs. This can be done through the modification of the optical depth of photons, or the induction of noise in the energy spectra of distant sources. This noise is the ALP-mediated counterpart of the turbulent nature of astrophysical magnetic fields. The study of these effect reveals a rich phenomenology, which I propose to review. Its application to observations, aiming at constraining the ALP parameter space, is very delicate because of the stochastic nature of the expected effects. I will show how these difficulties can be worked out and present results obtained from observations with Chandra and H.E.S.S., as well as some prospects.
Contact : ccaprini